U.S. patent application number 15/382433 was filed with the patent office on 2017-06-29 for methods and apparatus for resource collision avoidance in vehicle to vehicle communication.
The applicant listed for this patent is Samsung Electronics Co., Ltd. Invention is credited to Thomas David Novlan, Aris Papasakellariou, Sridhar Rajagopal.
Application Number | 20170188391 15/382433 |
Document ID | / |
Family ID | 59088146 |
Filed Date | 2017-06-29 |
United States Patent
Application |
20170188391 |
Kind Code |
A1 |
Rajagopal; Sridhar ; et
al. |
June 29, 2017 |
METHODS AND APPARATUS FOR RESOURCE COLLISION AVOIDANCE IN VEHICLE
TO VEHICLE COMMUNICATION
Abstract
The sensing method a first vehicle user equipment (UE) for
collision avoidance in a wireless communication network comprises
receiving a set of scheduling assignment (SA) information allocated
to a set of second vehicle UEs, decoding the set of SA information,
each of which includes SA information to each of the set of second
vehicle UEs, performing energy sensing operation for resources to
be used by each of the set of second vehicle UEs to determine
additional potential SA transmission and data transmission from the
set of second vehicle UEs over the resources, determining available
resources for the data transmission from the first vehicle UE based
on the performed energy sensing and SA sensing, skipping a channel
sensing operation on at least one subframe that is used for the
data transmission from the first vehicle UE, and transmitting data
among resources identified as unused in next transmissions from
second vehicle UEs.
Inventors: |
Rajagopal; Sridhar; (Plano,
TX) ; Novlan; Thomas David; (Dallas, TX) ;
Papasakellariou; Aris; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd |
Suwon-si |
|
KR |
|
|
Family ID: |
59088146 |
Appl. No.: |
15/382433 |
Filed: |
December 16, 2016 |
Related U.S. Patent Documents
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Application
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62272045 |
Dec 28, 2015 |
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62291211 |
Feb 4, 2016 |
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62291230 |
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Mar 18, 2016 |
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62319610 |
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62319053 |
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62320692 |
Apr 11, 2016 |
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62332818 |
May 6, 2016 |
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62332851 |
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62339551 |
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62346220 |
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62349338 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/121 20130101;
H04W 74/0816 20130101; H04W 52/383 20130101; H04W 28/0284 20130101;
H04W 84/18 20130101; H04W 76/14 20180201 |
International
Class: |
H04W 74/08 20060101
H04W074/08; H04W 28/02 20060101 H04W028/02; H04W 72/04 20060101
H04W072/04 |
Claims
1. An apparatus of a first vehicle user equipment (UE) for
collision avoidance using channel sensing in a wireless
communication network, the apparatus comprising: a transceiver
configured to receive a set of scheduling assignment (SA)
information that is allocated to a set of second vehicle UEs in the
wireless communication network; and at least one processor
configured to: decode the set of SA information each of which
includes SA information to each of the set of second vehicle UEs;
perform energy sensing operation for resources to be used by each
of the set of second vehicle UEs to determine additional potential
SA transmission and data transmission from the set of second
vehicle UEs over the resources; determine available resources for
the data transmission from the first vehicle UE based on the
performed energy sensing and SA sensing; and skip a channel sensing
operation on at least one subframe that is used for the data
transmission from the first vehicle UE based on a result of the
determination of available resources, wherein the transceiver is
further configured to transmit data among resources identified as
unused in next transmissions from second vehicle UEs.
2. The apparatus of claim 1, wherein the at least one processor is
further configured to: exclude unavailable data resources based on
the decoded set of SA information for the data transmission from
the first vehicle UE; and select the available resources for the
data transmission from the first vehicle UE based on the decoded
set of SA information.
3. The apparatus of claim 1, wherein the at least one processor is
further configured to: determine a set of transmission parameters
based on the available resources; and perform the data transmission
from the first vehicle UE on the available resources in accordance
with a set of transmission parameters.
4. The apparatus of claim 3, wherein the set of transmission
parameters comprises at least one of a transmit power, a modulation
and coding scheme (MCS), or semi-persistent related parameters
including a next transmission interval.
5. The apparatus of claim 1, wherein the set of SA information is
received on pre-determined frequency resources.
6. The apparatus of claim 1, wherein the at least one processor is
further configured to: determine a sensing duration for the channel
sensing operation based on a sensing window period that is a same
for transmissions from a plurality of UEs in a given resource pool;
and identify a resource availability map for next data transmission
based on sensing during a result of the determination of sensing
duration.
7. The apparatus of claim 1, wherein the at least one processor is
further configured to: determine whether the data transmission is
continued on the available resources; and trigger reselection of
the available resources for the data transmission when a condition
has been satisfied.
8. The apparatus of claim 7, wherein the condition is satisfied
with at least one of: a counter has been expired, the counter for
each UE being independently reset or initialized to a value
randomly chosen within a pre-determined range of values; or the
first vehicle UE identifies that a transport block (TB) included in
the data transmission does not fit within an available resource
allocation using an allowable MCS.
9. The apparatus of claim 1, wherein a next transmission at n+e is
offset from a currently scheduled transmission n+d in a multiple of
period P e=k*P.sub.min+d, and wherein k is an integer in range 0 to
10 and P.sub.min is set to 100, the k being indicated in an SCI as
e-d using 4 bits.
10. The apparatus of claim 1, wherein a congestion level observed
by the first vehicle UE is defined by at least one of a percentage
of unavailable data or SA resources observed by the first vehicle
UE based on sensing and is used for resource allocation, and
wherein a congestion percentage is defined as a ratio of a number
of busy resources in T and a number of total resources in T, and
wherein T is a measuring interval, the congestion level being
indicated to the eNB based on an eNB request.
11. The apparatus of claim 1, wherein if a sub-frame m is skipped
for sensing by the first vehicle UE, a resource selection in
subframes at m+k*P.sub.min is avoided until a sensing operation is
performed in next sub-frame m+k*P.sub.min, and wherein k is an
integer and k>0 and P.sub.min is set to 100.
12. The apparatus of claim 11, wherein the first vehicle UE
performs sensing in sub-frames m-k*P.sub.min, and wherein k is an
integer in range of 1.ltoreq.k.ltoreq.10 and P.sub.min is set to
100.
13. An apparatus of an eNodeB (eNB) for collision avoidance using
channel sensing in a wireless communication network, the apparatus
comprises: at least one processor configured to determine a set of
scheduling assignment information (SA) including at least one of an
allocation identifier (ID) or a periodicity; a transceiver
configured to: transmit the SA information to a set of UEs in the
wireless communication network; transmit a congestion level request
to the set of UEs; and receive, from the set of UEs, a congestion
level response corresponding to the congestion level request,
wherein the congestion level response includes a congestion
percentage based on a ratio of a number of busy resources and a
number of total resources.
14. The apparatus of claim 13, wherein the at least one processor
is further configured to activate or de-activate the SA information
at every subframe using downlink control information (DCI).
15. The apparatus of claim 13, wherein: the at least one processor
is further configured to determine a threshold that is statically
configured for an energy measurement operation by the set of UEs;
and the transceiver is further configured to transmit the threshold
to the set of UEs in the wireless communication network.
16. The apparatus of claim 13, wherein the at least one processor
is further configured to transmit a request to receive a network
load measurement report from the set of UEs in the wireless
communication network, the network load measurement report being
used to select at least one path for a vehicle-to-vehicle (V2V)
communication.
17. A sensing method of a first vehicle user equipment (UE) for
collision avoidance using channel sensing in a wireless
communication network, the sensing method comprising: receiving a
set of scheduling assignment (SA) information that is allocated to
a set of second vehicle UEs in the wireless communication network;
decoding the set of SA information each of which includes SA
information to each of the set of second vehicle UEs; performing
energy sensing operation for resources to be used by each of the
set of second vehicle UEs to determine additional potential SA
transmission and data transmission from the set of second vehicle
UEs over the resources; determining available resources for the
data transmission from the first vehicle UE based on the performed
energy sensing and SA sensing; skipping a channel sensing operation
on at least one subframe that is used for the data transmission
from the first vehicle UE based on a result of the determination of
available resources; and transmitting data among resources
identified as unused in next transmissions from second vehicle
UEs.
18. The sensing method of claim 17, further comprising: excluding
unavailable data resources based on the decoded set of SA
information for the data transmission from the first vehicle UE;
and selecting the available resources for the data transmission
from the first vehicle UE based on the decoded set of SA
information.
19. The sensing method of claim 17, further comprising: determining
a set of transmission parameters based on the available resources;
and performing the data transmission from the first vehicle UE on
the available resources in accordance with a set of transmission
parameters.
20. The sensing method of claim 19, wherein the set of transmission
parameters comprises at least one of a transmit power, a modulation
and coding scheme (MCS), or semi-persistent related parameters
including a next transmission interval.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to: [0002] U.S. Provisional Patent Application No.
62/272,045 filed on Dec. 28, 2015 entitled METHOD AND APPARATUS FOR
SYNCHRONIZATION IN VEHICLE TO VEHICLE COMMUNICATION; [0003] U.S.
Provisional Patent Application No. 62/291,211 filed on Feb. 4, 2016
entitled METHOD AND APPARATUS FOR SYNCHRONIZATION IN VEHICLE TO
VEHICLE COMMUNICATION; [0004] U.S. Provisional Patent Application
No. 62/291,230 filed on Feb. 4, 2016 entitled METHOD AND APPARATUS
FOR COLLISION AVOIDANCE IN VEHICLE TO VEHICLE COMMUNICATION; [0005]
U.S. Provisional Patent Application No. 62/296,320 filed on Feb.
17, 2016 entitled METHOD AND APPARATUS FOR SYNCHRONIZATION IN
VEHICLE TO VEHICLE COMMUNICATION; [0006] U.S. Provisional Patent
Application No. 62/310,323 filed on Mar. 18, 2016 entitled METHOD
AND APPARATUS FOR COLLISION AVOIDANCE IN VEHICLE TO VEHICLE
COMMUNICATION; [0007] U.S. Provisional Patent Application No.
62/319,610 filed on Apr. 7, 2016 entitled METHOD AND APPARATUS FOR
COLLISION AVOIDANCE IN VEHICLE TO VEHICLE COMMUNICATION; [0008]
U.S. Provisional Patent Application No. 62/319,053 filed on Apr. 6,
2016 entitled METHOD AND APPARATUS FOR SYNCHRONIZATION IN VEHICLE
TO VEHICLE COMMUNICATION; [0009] U.S. Provisional Patent
Application No. 62/320,692 filed on Apr. 11, 2016 entitled METHOD
AND APPARATUS FOR SYNCHRONIZATION IN VEHICLE TO VEHICLE
COMMUNICATION; [0010] U.S. Provisional Patent Application No.
62/332,818 filed on May 6, 2016 entitled METHOD AND APPARATUS FOR
SYNCHRONIZATION IN VEHICLE TO VEHICLE COMMUNICATION; [0011] U.S.
Provisional Patent Application No. 62/332,851 filed on May 6, 2016
entitled METHOD AND APPARATUS FOR COLLISION AVOIDANCE IN VEHICLE TO
VEHICLE COMMUNICATION; [0012] U.S. Provisional Patent Application
No. 62/339,551 filed on May 20, 2016 entitled METHOD AND APPARATUS
FOR COLLISION AVOIDANCE IN VEHICLE TO VEHICLE COMMUNICATION; [0013]
U.S. Provisional Patent Application No. 62/340,372 filed on May 23,
2016 entitled METHOD AND APPARATUS FOR COLLISION AVOIDANCE IN
VEHICLE TO VEHICLE COMMUNICATION; [0014] U.S. Provisional Patent
Application No. 62/346,220 filed on Jun. 6, 2016 entitled METHOD
AND APPARATUS FOR COLLISION AVOIDANCE IN VEHICLE TO VEHICLE
COMMUNICATION; and [0015] U.S. Provisional Patent Application No.
62/349,338 filed on Jun. 13, 2016 entitled METHOD AND APPARATUS FOR
COLLISION AVOIDANCE IN VEHICLE TO VEHICLE COMMUNICATION; The
above-identified provisional patent applications are hereby
incorporated by reference in their entirety.
TECHNICAL FIELD
[0016] This disclosure relates generally to wireless communication
systems. More specifically, this disclosure relates to method and
apparatus for resource collision avoidance in vehicle to vehicle
communication.
BACKGROUND
[0017] Traditionally, cellular communication networks have been
designed to establish wireless communication links between mobile
devices and fixed communication infrastructure components (such as
base stations or access points) that serve users in a wide or local
geographic range. However, a wireless network can also be
implemented to utilize only device-to-device (D2D) communication
links without a need for fixed infrastructure components. This type
of network is typically referred to as an ad-hoc network. A hybrid
communication network can support devices that connect both to
fixed infrastructure components and to other D2D-enabled devices.
While end user devices such as smartphones may be envisioned for
D2D communication networks, a vehicular communication network, such
as vehicle to everything (V2X) may be supported by a communication
protocol where vehicles exchange control and data information
between other vehicles (vehicle to vehicle (V2V)) or other
infrastructure (vehicle to infrastructure (V21)) and end-user
devices (vehicle to pedestrian (V2P)). Multiple types of
communication links may be supported by nodes providing V2X
communication in a network, and utilizing the same or different
protocols and systems.
SUMMARY
[0018] This disclosure provides a method and apparatus for resource
collision avoidance in vehicle to vehicle communication.
[0019] In one embodiment, an apparatus of a first vehicle user
equipment (UE) for collision avoidance using channel sensing in a
wireless communication network is provided. The apparatus comprises
a transceiver configured to receive a set of scheduling assignment
(SA) information that is allocated to a set of second vehicle UEs
in the wireless communication network. The apparatus further
comprises at least one processor configured to decode the set of SA
information each of which includes SA information to each of the
set of second vehicle UEs, perform energy sensing operation for
resources to be used by each of the set of second vehicle UEs to
determine additional potential SA transmission and data
transmission from the set of second vehicle UEs over the resources,
determine available resources for the data transmission from the
first vehicle UE based on the performed energy sensing and SA
sensing, and skip a channel sensing operation on at least one
subframe that is used for the data transmission from the first
vehicle UE based on a result of the determination of available
resources, wherein the transceiver is further configured to
transmit data among resources identified as unused in next
transmissions from second vehicle UEs.
[0020] In another embodiment, an apparatus of an eNodeB (eNB) for
collision avoidance using channel sensing in a wireless
communication network is provided. The apparatus comprises at least
one processor configured to determine a set of scheduling
assignment information (SA) including at least one of an allocation
identifier (ID) or a periodicity. The apparatus further comprises a
transceiver configured to transmit the SA information to a set of
UEs in the wireless communication network, transmit a congestion
level request to the set of UEs, and receive, from the set of UEs,
a congestion level response corresponding to the congestion level
request, wherein the congestion level response includes a
congestion percentage based on a ratio of a number of busy
resources and a number of total resources.
[0021] In yet another embodiment, a sensing method of a first
vehicle user equipment (UE) for collision avoidance using channel
sensing in a wireless communication network is provided. The
sensing method comprises receiving a set of scheduling assignment
(SA) information that is allocated to a set of second vehicle UEs
in the wireless communication network, decoding the set of SA
information each of which includes SA information to each of the
set of second vehicle UEs, performing energy sensing operation for
resources to be used by each of the set of second vehicle UEs to
determine additional potential SA transmission and data
transmission from the set of second vehicle UEs over the resources,
determining available resources for the data transmission from the
first vehicle UE based on the performed energy sensing and SA
sensing, skipping a channel sensing operation on at least one
subframe that is used for the data transmission from the first
vehicle UE based on a result of the determination of available
resources, and transmitting data among resources identified as
unused in next transmissions from second vehicle UEs.
[0022] Other technical features may be readily apparent to one
skilled in the art from the following figures, descriptions, and
claims.
[0023] Before undertaking the DETAILED DESCRIPTION below, it may be
advantageous to set forth definitions of certain words and phrases
used throughout this patent document. The term "couple" and its
derivatives refer to any direct or indirect communication between
two or more elements, whether or not those elements are in physical
contact with one another. The terms "transmit," "receive," and
"communicate," as well as derivatives thereof, encompass both
direct and indirect communication. The terms "include" and
"comprise," as well as derivatives thereof, mean inclusion without
limitation. The term "or" is inclusive, meaning and/or. The phrase
"associated with," as well as derivatives thereof, means to
include, be included within, interconnect with, contain, be
contained within, connect to or with, couple to or with, be
communicable with, cooperate with, interleave, juxtapose, be
proximate to, be bound to or with, have, have a property of, have a
relationship to or with, or the like. The term "controller" means
any device, system or part thereof that controls at least one
operation. Such a controller may be implemented in hardware or a
combination of hardware and software and/or firmware. The
functionality associated with any particular controller may be
centralized or distributed, whether locally or remotely. The phrase
"at least one of," when used with a list of items, means that
different combinations of one or more of the listed items may be
used, and only one item in the list may be needed. For example, "at
least one of: A, B, and C" includes any of the following
combinations: A, B, C, A and B, A and C, B and C, and A and B and
C.
[0024] Moreover, various functions described below can be
implemented or supported by one or more computer programs, each of
which is formed from computer readable program code and embodied in
a computer readable medium. The terms "application" and "program"
refer to one or more computer programs, software components, sets
of instructions, procedures, functions, objects, classes,
instances, related data, or a portion thereof adapted for
implementation in a suitable computer readable program code. The
phrase "computer readable program code" includes any type of
computer code, including source code, object code, and executable
code. The phrase "computer readable medium" includes any type of
medium capable of being accessed by a computer, such as read only
memory (ROM), random access memory (RAM), a hard disk drive, a
compact disc (CD), a digital video disc (DVD), or any other type of
memory. A "non-transitory" computer readable medium excludes wired,
wireless, optical, or other communication links that transport
transitory electrical or other signals. A non-transitory computer
readable medium includes media where data can be permanently stored
and media where data can be stored and later overwritten, such as a
rewritable optical disc or an erasable memory device.
[0025] Definitions for other certain words and phrases are provided
throughout this patent document. Those of ordinary skill in the art
should understand that in many if not most instances, such
definitions apply to prior as well as future uses of such defined
words and phrases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] For a more complete understanding of this disclosure and its
advantages, reference is now made to the following description,
taken in conjunction with the accompanying drawings, in which:
[0027] FIG. 1 illustrates an example wireless network according to
embodiments of the present disclosure;
[0028] FIG. 2 illustrates an example base station (BS) according to
embodiments of the present disclosure;
[0029] FIG. 3 illustrates an example user equipment (UE) according
to embodiments of the present disclosure;
[0030] FIG. 4 illustrates an example long-term evolution vehicle
(LTE V2X) communication network according to embodiments of the
present disclosure;
[0031] FIG. 5 illustrate an example sidelink (SL) interface
according to embodiments of the present disclosure;
[0032] FIG. 6 illustrates an example resource pool for a physical
downlink shared control channel (PDSCCH) according to embodiments
of the present disclosure;
[0033] FIG. 7 illustrates an example resource pools for several
modes and traffics according to embodiments of the present
disclosure;
[0034] FIG. 8 illustrates an example procedure for a mode 2
operation with network assistance according to embodiments of the
present disclosure;
[0035] FIG. 9 illustrates an example procedure for a mode 2
operation without network assistance according to embodiments of
the present disclosure;
[0036] FIG. 10 illustrates an example transmission power adaptation
based on traffic conditions according to embodiments of the present
disclosure;
[0037] FIG. 11 illustrates an example device-to-device (D2D) and
vehicle-to-vehicle (V2V) subframes according to embodiments of the
present disclosure;
[0038] FIG. 12 illustrates an example collision avoidance method
according to embodiments of the present disclosure;
[0039] FIG. 13 illustrates an example adjustment of power sensing
result with transmit power according to embodiments of the present
disclosure;
[0040] FIG. 14 illustrates an example method for sensing based on
scheduling assignment (SA) decoding and energy measurement
according to embodiments of the present disclosure;
[0041] FIG. 15 illustrates an example sensing duration according to
embodiments of the present disclosure;
[0042] FIG. 16 illustrates an example sensing result in different
subframes (SF) according to embodiments of the present
disclosure;
[0043] FIG. 17 illustrates an example a number of SA transmission
according to embodiments of the present disclosure;
[0044] FIG. 18 illustrates an example sensing based on SA scan and
energy saving according to embodiments of the present
disclosure;
[0045] FIG. 19 illustrates an example energy scan on different
periodicities and event trigged traffics according to embodiments
of the present disclosure;
[0046] FIG. 20 illustrates an example power adjustment based on
sensing results according to embodiments of the present
disclosure;
[0047] FIG. 21 illustrates an example resource utilization overload
according to embodiments of the present disclosure;
[0048] FIG. 22 illustrates an example period of a semi-persistent
transmission of SA and data according to embodiments of the present
disclosure;
[0049] FIG. 23 illustrates an example a number of transmission
selections according to embodiments of the present disclosure;
[0050] FIG. 24 illustrates an example method for selecting PSCCH
resources according to embodiments of the present disclosure;
[0051] FIG. 25 illustrates an example resource selection procedure
according to embodiments of the present disclosure;
[0052] FIG. 26 illustrates an example operation of multiple
resource pools (RPs) according to embodiments of the present
disclosure; and
[0053] FIG. 27 illustrates an example transmit power per resource
block according to embodiments of the present disclosure;
[0054] FIG. 28 illustrates an example synchronization subframe (SF)
structure according to embodiments of the present disclosure;
[0055] FIG. 29 illustrates an example transmitter for
synchronization operation in vehicle-to-vehicle (V2V)
communications according to embodiments of the present
disclosure;
[0056] FIG. 30 illustrates an example receiver for synchronization
operation in vehicle-to-vehicle (V2V) communications according to
embodiments of the present disclosure;
[0057] FIG. 31 illustrates an example channel coherence time
according to embodiments of the present disclosure;
[0058] FIG. 32 illustrates an example V2V and D2D network operation
according to embodiments of the present disclosure;
[0059] FIG. 33 illustrates another example V2V and D2D network
operation according to embodiments of the present disclosure;
[0060] FIG. 34 illustrates an example physical sidelink broadcast
channel (PSBCH) SF structure. V2V according to embodiments of the
present disclosure;
[0061] FIG. 35 illustrates an example PSBCH SF structure with
additional demodulation reference signal DMRS) symbols according to
embodiments of the present disclosure;
[0062] FIG. 36 illustrates another example PSBCH SF structure with
additional DMRS symbols according to embodiments of the present
disclosure;
[0063] FIG. 37 illustrates yet another example PSBCH SF structure
with additional DMRS symbols according to embodiments of the
present disclosure;
[0064] FIG. 38 illustrates another example PSBCH SF structure
according to embodiments of the present disclosure;
[0065] FIG. 39 illustrates yet another example PSBCH SF structure
with additional DMRS symbols according to embodiments of the
present disclosure;
[0066] FIG. 40 illustrates yet another example PSBCH SF structure
with additional DMRS symbols according to embodiments of the
present disclosure;
[0067] FIG. 41 illustrates yet another example PSBCH SF structure
with additional DMRS symbols according to embodiments of the
present disclosure; and
[0068] FIG. 42 illustrates an example DMRS configuration for
physical sidelink shared channel (PSSCH) and physical sidelink
control channel (PSCCH) according to embodiments of the present
disclosure.
DETAILED DESCRIPTION
[0069] FIGS. 1 through 42, discussed below, and the various
embodiments used to describe the principles of this disclosure in
this patent document are by way of illustration only and should not
be construed in any way to limit the scope of the disclosure. Those
skilled in the art will understand that the principles of this
disclosure may be implemented in any suitably arranged wireless
communication system.
The following documents and standards descriptions are hereby
incorporated by reference into the present disclosure as if fully
set forth herein: 3GPP TS 36.211 v13.0, "E-UTRA, Physical channels
and modulation" (REF 1); 3GPP TS 36.212 v13.0, "E-UTRA,
Multiplexing and Channel coding" (REF 2); 3GPP TS 36.213 v13.0,
"E-UTRA, Physical Layer Procedures" (REF 3); 3GPP TS 36.321 v13.0,
"E-UTRA, Medium Access Control (MAC) protocol specification" (REF
4); 3GPP TS36.331 v13.0.0, "E-UTRA, Radio Resource Control (RRC)
protocol specification" (REF 5); 3GPP TS 23.303, "v13.2.0,
"Proximity-based services (ProSe); stage 2" (REF 6); 3GPP TS 22.885
v2.0, 0, "Study on LTE support for V2X services" (REF 7); 3GPP
R1-156932, "Collision avoidance for Mode 2"; and 3GPP R1-156429''
(REF 8); and 3GPP R1-156429, "Power control for V2V" (REF 9).
[0070] The descriptions of FIGS. 1-3 are not meant to imply
physical or architectural limitations to the manner in which
different embodiments may be implemented. Different embodiments of
the present disclosure may be implemented in any suitably-arranged
communications system.
[0071] To meet the demand for wireless data traffic having
increased since deployment of 4G communication systems, efforts
have been made to develop an improved 5G or pre-5G communication
system. Therefore, the 5G or pre-5G communication system is also
called a `Beyond 4G Network` or a `Post LTE System` or `New Radio
Access Technology (NR)`.
[0072] The 5G communication system is considered to be implemented
in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to
accomplish higher data rates. To decrease propagation loss of the
radio waves and increase the transmission distance, the
beamforming, massive multiple-input multiple-output (MIMO), Full
Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming,
large scale antenna techniques are discussed in 5G communication
systems.
[0073] In addition, in 5G communication systems, development for
system network improvement is under way based on advanced small
cells, cloud Radio Access Networks (RANs), ultra-dense networks,
device-to-device (D2D) communication, wireless backhaul, moving
network, cooperative communication, Coordinated Multi-Points
(CoMP), reception-end interference cancellation and the like.
[0074] In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and
sliding window superposition coding (SWSC) as an advanced coding
modulation (ACM), and filter bank multi carrier (FBMC),
non-orthogonal multiple access (NOMA), and sparse code multiple
access (SCMA) as an advanced access technology have been
developed.
[0075] FIG. 1 illustrates an example wireless network 100 according
to embodiments of the present disclosure. The embodiment of the
wireless network 100 shown in FIG. 1 is for illustration only.
Other embodiments of the wireless network 100 could be used without
departing from the scope of this disclosure.
[0076] As shown in FIG. 1, the wireless network 100 includes a BS
101, a BS 102, and a BS 103. The BS 101 communicates with the BS
102 and the BS 103. The BS 101 also communicates with at least one
network 130, such as the Internet, a proprietary Internet Protocol
(IP) network, or other data network.
[0077] The BS 102 provides wireless broadband access to the network
130 for a first plurality of UEs within a coverage area 120 of the
BS 102. The first plurality of UEs includes a UE 111, which may be
located in a small business (SB); a UE 112, which may be located in
an enterprise (E); a UE 113, which may be located in a WiFi hotspot
(HS); a UE 114, which may be located in a first residence (R); a UE
115, which may be located in a second residence (R); and a UE 116,
which may be a mobile device (M), such as a cell phone, a wireless
laptop, a wireless PDA, or the like. The BS 103 provides wireless
broadband access to the network 130 for a second plurality of UEs
within a coverage area 125 of the BS 103. The second plurality of
UEs includes the UE 115 and the UE 116. In some embodiments, one or
more of the BSs 101-103 may communicate with each other and with
the UEs 111-116 using 5G, LTE, LTE-A, WiMAX, WiFi, LTE-U(LAA),
device-to device (D2D), vehicle communication (V2X) such as
vehicle-to-device (V2P), vehicle-to-infrastructure (V2I),
vehicle-to-vehicle (V2V), or other wireless communication
techniques. In one embodiment, the BSs 101-103 may be implemented
as managing entities that control the UEs 111-116 (such as vehicle
terminals).
[0078] Depending on the network type, other well-known terms may be
used instead of "eNodeB" or "eNB," such as "base station",
"managing entity", "managing network entity", or "access point."
For the sake of convenience, the terms "eNodeB" and "eNB" are used
in this patent document to refer to network infrastructure
components that provide wireless access to remote terminals. Also,
depending on the network type, other well-known terms may be used
instead of "user equipment" or "UE," such as "mobile station,"
"subscriber station," "remote terminal," "wireless terminal,"
"vehicle" or "user device." For the sake of convenience, the terms
"user equipment" and "UE" are used in this patent document to refer
to remote wireless equipment that wirelessly accesses an eNB (such
as base station), whether the UE is a mobile device (such as a
vehicle terminal, a mobile telephone, or smartphone) or is normally
considered a stationary device (such as a desktop computer, or
vending machine).
[0079] Dotted lines show the approximate extents of the coverage
areas 120 and 125, which are shown as approximately circular for
the purposes of illustration and explanation only. It should be
clearly understood that the coverage areas associated with BSs,
such as the coverage areas 120 and 125, may have other shapes,
including irregular shapes, depending upon the configuration of the
BSs and variations in the radio environment associated with natural
and man-made obstructions.
[0080] As described in more detail below, one or more of the UEs
111-116 (such as a vehicle with a wireless communication interface,
also may be termed as vehicle UE) include circuitry, programming,
or a combination thereof, for processing of the control
information, also known as scheduling assignment (SA) information
and data transmission for collision avoidance in a wireless
communication network (e.g., vehicle to vehicle (V2V) communication
network). In certain embodiments, and one or more of the BSs
101-103 (e.g., eNB, E-UTRAN) includes circuitry, programming, or a
combination thereof, for determining a set of SA information each
of which includes SA information to each of a set of vehicle UEs
and determining available resources for data transmission from the
set of vehicle UEs based on the set of SA information. In one
embodiment, one or more of the BSs 101-103 transmits the set of SA
information to the set of vehicle UEs in the wireless communication
network. The set of SA information is transmitted on pre-determined
frequency resources.
[0081] Although FIG. 1 illustrates one example of a wireless
network 100, various changes may be made to FIG. 1. For example,
the wireless network 100 could include any number of BSs (such as
managing entities) and any number of UEs (such as vehicle
terminals) in any suitable arrangement. Also, the BS 101 could
communicate directly with any number of UEs and provide those UEs
with wireless broadband access to the network 130. Similarly, each
BS 102-103 could communicate directly with the network 130 and
provide UEs with direct wireless broadband access to the network
130. Further, the BSs 101, 102, and/or 103 could provide access to
other or additional external networks, such as external telephone
networks or other types of data networks.
[0082] FIG. 2 illustrates an example BS 102 according to
embodiments of the present disclosure. The embodiment of the BS 102
illustrated in FIG. 2 is for illustration only, and the BSs 101 and
103 of FIG. 1 could have the same or similar configuration.
However, BSs come in a wide variety of configurations, and FIG. 2
does not limit the scope of this disclosure to any particular
implementation of a BS. In one embodiment, the BSs may be
implemented as eNodeB (eNB) or E-UTRAN or transmit reception point
(TRP) in a V2X communication network.
[0083] As shown in FIG. 2, the BS 102 includes multiple antennas
205a-205n, multiple RF transceivers 210a-210n, transmit (TX)
processing circuitry 215, and receive (RX) processing circuitry
220. The BS 102 also includes a controller/processor 225, a memory
230, and a backhaul or network interface 235.
[0084] The RF transceivers 210a-210n receive, from the antennas
205a-205n, incoming RF signals, such as signals transmitted by UEs
in the network 100. In one embodiment, the UEs may be implemented
as vehicle terminals in a V2X communication network. The RF
transceivers 210a-210n down-convert the incoming RF signals to
generate IF or baseband signals. The IF or baseband signals are
sent to the RX processing circuitry 220, which generates processed
baseband signals by filtering, decoding, and/or digitizing the
baseband or IF signals. The RX processing circuitry 220 transmits
the processed baseband signals to the controller/processor 225 for
further processing.
[0085] In some embodiment, the RF transceivers 210a-210n is
configured to transmit the SA information to a set of UEs in the
wireless communication network. In some embodiment, the RF
transceivers 210a-210n is configured to transmit a congestion level
request to the set of UEs and receive, from the set of UEs, a
congestion level response corresponding to the congestion level
request, wherein the congestion level response includes a
congestion percentage based on a ratio of a number of busy
resources and a number of total resources.
[0086] In some embodiment, the RF transceivers 210a-210n is
configured to transmit the threshold to the set of UEs in the
wireless communication network.
[0087] The TX processing circuitry 215 receives analog or digital
data (such as voice data, web data, e-mail, or interactive video
game data) from the controller/processor 225. The TX processing
circuitry 215 encodes, multiplexes, and/or digitizes the outgoing
baseband data to generate processed baseband or IF signals. The RF
transceivers 210a-210n receive the outgoing processed baseband or
IF signals from the TX processing circuitry 215 and up-converts the
baseband or IF signals to RF signals that are transmitted via the
antennas 205a-205n. In some embodiment, the RF transceivers
210a-210n are configured to transmit the set of SA information to
the set of vehicle UEs in the wireless communication network.
[0088] The controller/processor 225 can include one or more
processors or other processing devices that control the overall
operation of the eNB 102. For example, the controller/processor 225
could control the reception of forward channel signals and the
transmission of reverse channel signals by the RF transceivers
210a-210n, the RX processing circuitry 220, and the TX processing
circuitry 215 in accordance with well-known principles. The
controller/processor 225 could support additional functions as
well, such as more advanced wireless communication functions. For
instance, the controller/processor 225 could support beam forming
or directional routing operations in which outgoing signals from
multiple antennas 205a-205n are weighted differently to effectively
steer the outgoing signals in a desired direction. Any of a wide
variety of other functions could be supported in the BS 102 by the
controller/processor 225. In some embodiments, the
controller/processor 225 includes at least one microprocessor or
microcontroller.
[0089] As described in more detail below, the BS 102 includes
circuitry, programming, or a combination thereof for collision
avoidance in V2X communication network. The BS 102 (e.g., eNB,
E-UTRAN) is configured to transmit the set of SA information to the
set of vehicle UEs in the wireless communication network.
[0090] In some embodiment, controller/processor 225 can be
configured to execute one or more instructions, stored in memory
230, that are configured to cause the controller/processor to
determine a set of scheduling assignment information (SA) including
at least one of an allocation identifier (ID) or a periodicity.
[0091] In some embodiment, controller/processor 225 can be
configured to execute one or more instructions, stored in memory
230, that are configured to cause the controller/processor to
activate or de-activate the SA information at every subframe using
downlink control information (DCI).
[0092] In some embodiment, controller/processor 225 can be
configured to execute one or more instructions, stored in memory
230, that are configured to cause the controller/processor to
determine a threshold that is statically configured for an energy
measurement operation by the set of UEs.
[0093] In some embodiment, controller/processor 225 can be
configured to execute one or more instructions, stored in memory
230, that are configured to cause the controller/processor to
transmit a request to receive a network load measurement report
from the set of UEs in the wireless communication network, the
network load measurement report being used to select at least one
path for a vehicle-to-vehicle (V2V) communication.
[0094] The controller/processor 225 is also capable of executing
programs and other processes resident in the memory 230, such as an
OS. The controller/processor 225 can move data into or out of the
memory 230 as required by an executing process.
[0095] The controller/processor 225 is also coupled to the backhaul
or network interface 235. The backhaul or network interface 235
allows the BS 102 to communicate with other devices or systems over
a backhaul connection or over a network. The interface 235 could
support communications over any suitable wired or wireless
connection(s). For example, when the BS 102 is implemented as part
of a cellular communication system (such as one supporting V2P,
V2I, V2V, D2D, 5G new radio access technology (NR), LTE, LTE-A, or
LAA), the interface 235 could allow the BS 102 to communicate with
other BSs over a wired or wireless backhaul connection. When the BS
102 is implemented as an access point, the interface 235 could
allow the BS 102 to communicate over a wired or wireless local area
network or over a wired or wireless connection to a larger network
(such as the Internet). The interface 235 includes any suitable
structure supporting communications over a wired or wireless
connection, such as an Ethernet or RF transceiver.
[0096] The memory 230 is coupled to the controller/processor 225.
Part of the memory 230 could include a RAM, and another part of the
memory 230 could include a flash memory or other ROM.
[0097] Although FIG. 2 illustrates one example of BS 102, various
changes may be made to FIG. 2. For example, the BS 102 could
include any number of each component shown in FIG. 2. As a
particular example, an access point could include a number of
interfaces 235, and the controller/processor 225 could support
routing functions to route data between different network
addresses. As another particular example, while shown as including
a single instance of TX processing circuitry 215 and a single
instance of RX processing circuitry 220, the BS 102 could include
multiple instances of each (such as one per RF transceiver). Also,
various components in FIG. 2 could be combined, further subdivided,
or omitted and additional components could be added according to
particular needs.
[0098] FIG. 3 illustrates an example UE 116 according to
embodiments of the present disclosure. The embodiment of the UE 116
illustrated in FIG. 3 is for illustration only, and the UEs 111-115
of FIG. 1 could have the same or similar configuration. However,
UEs come in a wide variety of configurations, and FIG. 3 does not
limit the scope of this disclosure to any particular implementation
of a UE. In one embodiment, the UE 116 may be implemented as a
vehicle terminal in a V2X communication network.
[0099] As shown in FIG. 3, the UE 116 includes a set of antennas
305, a radio frequency (RF) transceiver 310, TX processing
circuitry 315, a microphone 320, and receive (RX) processing
circuitry 325. The UE 116 also includes a speaker 330, a processor
340, an input/output (I/O) interface (IF) 345, an input device 350,
a display 355, and a memory 360. The memory 360 includes an
operating system (OS) 361 and one or more applications 362.
[0100] The RF transceiver 310 receives, from the set of antennas
305, an incoming RF signal transmitted by an eNB of the network
100. The RF transceiver 310 down-converts the incoming RF signal to
generate an intermediate frequency (IF) or baseband signal. In some
embodiment, the RF transceiver 310 receives a transceiver
configured to transmit an authorization request message to a
managing entity and receive an authorization confirmation message
corresponding to the authorization request message from the
managing entity. In some embodiments, the RF transceiver 310
receives a plurality of messages including control and data
messages from the at least one second UE.
[0101] In some embodiments, the RF transceiver 310 is configure to
receive a set of scheduling assignment (SA) information that is
allocated to a set of second vehicle UEs in the wireless
communication network; and
[0102] The IF or baseband signal is sent to the RX processing
circuitry 325, which generates a processed baseband signal by
filtering, decoding, and/or digitizing the baseband or IF signal.
The RX processing circuitry 325 transmits the processed baseband
signal to the speaker 330 (such as for voice data) or to the
processor 340 for further processing (such as for web browsing
data).
[0103] The TX processing circuitry 315 receives analog or digital
voice data from the microphone 320 or other outgoing baseband data
(such as web data, e-mail, or interactive video game data) from the
processor 340. The TX processing circuitry 315 encodes,
multiplexes, and/or digitizes the outgoing baseband data to
generate a processed baseband or IF signal. The RF transceiver 310
receives the outgoing processed baseband or IF signal from the TX
processing circuitry 315 and up-converts the baseband or IF signal
to an RF signal that is transmitted via the antenna 305.
[0104] The processor 340 can include one or more processors or
other processing devices and execute the OS 361 stored in the
memory 360 in order to control the overall operation of the UE 116.
For example, the processor 340 could control the reception of
forward channel signals and the transmission of reverse channel
signals by the RF transceiver 310, the RX processing circuitry 325,
and the TX processing circuitry 315 in accordance with well-known
principles. In some embodiments, the processor 340 includes at
least one microprocessor or microcontroller.
[0105] In some embodiments, the processor 340 is also capable of
decoding the set of SA information each of which includes SA
information to each of the set of second vehicle UEs, performing
energy sensing operation for resources to be used by each of the
set of second vehicle UEs to determine additional potential SA
transmission and data transmission from the set of second vehicle
UEs over the resources, determining available resources for the
data transmission from the first vehicle UE based on the performed
energy sensing and SA sensing, and skipping a channel sensing
operation on at least one subframe that is used for the data
transmission from the first vehicle UE based on a result of the
determination of available resources, wherein the transceiver is
further configured to transmit data among resources identified as
unused in next transmissions from second vehicle UEs.
[0106] In some embodiments, the processor 340 is also capable of
excluding unavailable data resources based on the decoded set of SA
information for the data transmission from the first vehicle UE and
selecting the available resources for the data transmission from
the first vehicle UE based on the decoded set of SA
information.
[0107] In some embodiments, the processor 340 is also capable of
determining a set of transmission parameters based on the available
resources and performing the data transmission from the first
vehicle UE on the available resources in accordance with a set of
transmission parameters. In such embodiments, the set of
transmission parameters comprises at least one of a transmit power,
a modulation and coding scheme (MCS), or semi-persistent related
parameters including a next transmission interval. In such
embodiments, the set of SA information is received on
pre-determined frequency resources.
[0108] In some embodiments, the processor 340 is also capable of
determining a sensing duration for the channel sensing operation
based on a sensing window period that is a same for transmissions
from a plurality of UEs in a given resource pool and identifying a
resource availability map for next data transmission based on
sensing during a result of the determination of sensing
duration.
[0109] In some embodiments, the processor 340 is also capable of
determining whether the data transmission is continued on the
available resources and triggering reselection of the available
resources for the data transmission when a condition has been
satisfied. In such embodiments, the condition is satisfied with at
least one of a counter has been expired, the counter for each UE
being independently reset or initialized to a value randomly chosen
within a pre-determined range of values or the first vehicle UE
identifies that a transport block (TB) included in the data
transmission does not fit within an available resource allocation
using an allowable MCS.
[0110] In such embodiments, a next transmission at n+e is offset
from a currently scheduled transmission n+d in a multiple of period
P e=k*P.sub.min+d, and wherein k is an integer in range 0 to 10 and
P.sub.min is set to 100, the k being indicated in an SCI as e-d
using 4 bits. In such embodiments, a congestion level observed by
the first vehicle UE is defined by at least one of a percentage of
unavailable data or SA resources observed by the first vehicle UE
based on sensing and is used for resource allocation, and wherein a
congestion percentage is defined as a ratio of a number of busy
resources in T and a number of total resources in T, and wherein T
is a measuring interval, the congestion level being indicated to
the eNB based on an eNB request.
[0111] In such embodiment, if a sub-frame m is skipped for sensing
by the first vehicle UE, a resource selection in subframes at
m+k*P.sub.min is avoided until a sensing operation is performed in
next sub-frame m+k*P.sub.min, and wherein k is an integer and
k>0 and P.sub.min is set to 100. In such embodiments, the first
vehicle UE performs sensing in sub-frames m-k*P.sub.min, and
wherein k is an integer in range of 1.ltoreq.k.ltoreq.10 and
P.sub.min is set to 100.
[0112] The processor 340 can move data into or out of the memory
360 as required by an executing process. In some embodiments, the
processor 340 is configured to execute the applications 362 based
on the OS 361 or in response to signals received from BS s or an
operator. The processor 340 is also coupled to the I/O interface
345, which provides the UE 116 with the ability to connect to other
devices, such as laptop computers and handheld computers. The I/O
interface 345 is the communication path between these accessories
and the processor 340.
[0113] The processor 340 is also coupled to the input device 350
and the display 355. The operator of the UE 116 can use the input
device 350 to enter data into the UE 116. The display 355 may be a
liquid crystal display, light emitting diode display, or other
display capable of rendering text and/or at least limited graphics,
such as from web sites.
[0114] The memory 360 is coupled to the processor 340. Part of the
memory 360 could include a random access memory (RAM), and another
part of the memory 360 could include a Flash memory or other
read-only memory (ROM).
[0115] Although FIG. 3 illustrates one example of UE 116, various
changes may be made to FIG. 3. For example, various components in
FIG. 3 could be combined, further subdivided, or omitted and
additional components could be added according to particular needs.
As a particular example, the processor 340 could be divided into
multiple processors, such as one or more central processing units
(CPUs) and one or more graphics processing units (GPUs). In another
example, the UE 116 may include only one antenna 305 or any number
of antennas 305. Also, while FIG. 3 illustrates the UE 116
configured as a mobile telephone or smartphone, UEs could be
configured to operate as other types of mobile or stationary
devices.
[0116] FIG. 4 illustrates an example long-term evolution vehicle
(LTE V2X, LTE V2V) communication network 400 according to
embodiments of the present disclosure. An embodiment of the LTE V2X
network 400 shown in FIG. 4 is for illustration only. Other
embodiments may be used without departing from the scope of the
present disclosure.
[0117] As illustrated in FIG. 4, V2X communication (e.g., V2V
communication) may be used to implement many kinds of services that
are complementary to the primary communication network or provide
new services based on the flexibility of the network topology. V2X
may support unicasting, broadcasting, or groupcasting is a
potential means for V2V communication where vehicles are able to
transmit messages to all in-range V2V-enabled devices or a subset
of devices which are members of particular group. A protocol may be
based on LTE-D2D or a specialized LTE-V2V protocol. V2X can support
V2I communication between one or more vehicles and an
infrastructure node (101-103) to provide cellular connectivity as
well as specialized services related to control and safety of
vehicular traffic. V2P communication for UE's 111-116 can be
supported as well, for example to provide safety services for
pedestrians or traffic management services. V2X multicast
communication can be used to provide safety and control messages to
large numbers of vehicles in an efficient fashion.
[0118] While vehicle devices may be able to support many different
communication protocols, and mandatory and optional features, since
the traffic types, QoS requirements, and deployment topologies are
distinct from other types of communication, the hardware/software
on a vehicle for supporting V2X may have a reduced or specialized
functionality compared to other devices. For example protocols
related to low-complexity, low-data rate, and/or low-latency,
machine-type communication protocols 404 may be supported (such as
traffic tracking beacons).
[0119] Satellite-based communication 405 may also be supported for
V2X networks for communication or positioning services.
Additionally networks may require devices to operate in near
simultaneous fashion when switching between V2X communications
modes. Vehicle-to-vehicle communication 412 may also be supported
for V2X networks for communication or positioning services.
[0120] V2X requires resource allocation mechanisms since multiple
V2X UEs may have a need to utilize the same time/frequency
resources as other V2X or cellular or D2D UEs. In addition to
resource allocation signaling for the transmitting UEs, in the case
of V2X, receiving UEs may also require resource allocation
signaling in order to determine which time/frequency resources to
monitor to receive the transmissions of one of more V2X UEs.
Different resource allocation granularity may need to be supported
depending on multiple factors including deployment scenarios (such
as in/outside network coverage) and traffic types (such as unicast,
groupcast, video, etc.).
[0121] Traditionally for centralized resource management, a central
controller (such as managing entity) like the eNB collects all the
channel state information of every UE in the cell and allocates the
available resources to maximize a throughput according to fairness
and power constraints. For UEs within network coverage, the eNB may
be responsible for allocating resources for a group of UEs. Based
on the eNB or autonomous resource selection, the transmitting UEs
can provide a scheduling assignment signaling indicating the
resources the Rx UEs monitor for reception of the data (e.g., this
is called as "Mode 1" resource allocation).
[0122] On the other hand, especially considering an out-of-network
coverage scenario, UEs can determine their resource allocation
independently in a distributed fashion (e.g., this is called as
"Mode 2" resource allocation). Simple random resource selection may
be considered as a baseline distributed approach with a low
overhead and scalability. One drawback of such an approach is that
collisions are possible among broadcasting UEs. Thus an implicit
coordination (such as energy sensing) and/or explicit coordination
(such as sensing based on scheduling assignment transmission) would
be required to prevent collisions and mitigate interference.
[0123] FIG. 5 illustrates an example sidelink (SL) interface 500
according to embodiments of the present disclosure. An embodiment
of the SL interface 500 shown in FIG. 5 is for illustration only.
Other embodiments may be used without departing from the scope of
the present disclosure. As shown in FIG. 5, the SL interface 500
comprises a plurality of UEs 501, 502, and E-UTRAN (e.g., eNB)
503.
[0124] While UL designates the link from UE 501 to eNB 503 and DL
designates the reverse direction, SL designates the radio links
over the PC5 interfaces between UE 501 and UEs 205. The UE 501
transmits a V2V message to a plurality of UEs 502 in the SL
interface. The SL communication happens directly without using the
eNB 503 technology and not traversing any network node (e.g.,
eNodeB 503). The PC5 interface re-uses existing frequency
allocation, regardless of the duplex mode (frequency division
duplex (FDD) or time division duplex (TDD).
[0125] To minimize hardware impact on a UE and especially on the
power amplifier of the UE, transmission of V2V links occurs in the
UL band in case of FDD. Similar, the PC5 interface uses SFs that
are reserved for UL transmission in TDD. The signal transmission is
based on single carrier frequency division multiple access
(SC-FDMA) that is also used for UL transmission. The new channels
can be largely based on the channel structure applicable for the
transmission of the physical UL shared channel (PUSCH).
[0126] A SL transmission and reception occurs with resources
assigned to a group of devices. A resource pool (RP) is a set of
resources assigned for SL operation. The RP comprises the subframes
and the resource blocks within the subframe. For SL communication,
two additional physical channels are introduced such as physical
sidelink control channel (PSCCH) carrying the control information
and physical sidelink shared channel (PSSCH) carrying the data.
[0127] FIG. 6 illustrates an example resource pool 600 for a
physical sidelink control Channel (PSCCH) according to embodiments
of the present disclosure. An embodiment of the resource pool 600
for the PSCCH shown in FIG. 6 is for illustration only. Other
embodiments may be used without departing from the scope of the
present disclosure. As shown in FIG. 6, the resource pool 600
comprises a PSCCH 605 and V2V 610 resources. The resource pool 600
is defined in frequency and time domains. In frequency domain,
PRBnum defines the frequency range in physical resource block (PRB)
bandwidth units, and PRBstart and PRBend define the location in the
frequency domain within the uplink band. In time domain, a bitmap
indicates the 1 millisecond (msec) sub-frames used for PSCCH
transmission. The block of resources is repeated with a period
defined by a parameter SC-Period (expressed in sub-frame duration,
i.e. 1 msec). The range of possible values for SC-Period is from 40
msec to 320 msec: low values are supported for voice
transmission.
[0128] All the parameters needed to define the resource pool are
broadcasted in a system information block (SIB) by the network. The
devices which are not within coverage (and hence cannot acquire the
SIB) may use some pre-configured values internally stored. The
PSCCH is used by the D2D/V2V transmitting UE to make the members of
the D2D/V2V group aware of the next data transmission that will
occur on the PSSCH. The D2D/V2V transmitting UE sends the SL
control information (SCI) on the PSCCH as shown in TABLE 1. The
PSCCH transmission is also called as the scheduling assignment (SA)
since it provides the schedule of the transmission of the UE.
TABLE-US-00001 TABLE 1 Parameter Usage Group destination used by
the receiving devices to determine ID whether they have some
interest in this announcement. If the identifier does not match,
they do not need to monitor SL channels until the next SC-Period
Modulation and to indicate modulation and coding rate for the
coding scheme (MCS) data Resource block give the receiving devices
information about the assignment and resources of the PSSCH that
they shall decode in hopping resource the frequency domain
allocation Frequency hopping flag Time resource give the receiving
devices information about the pattern (T-RPT) resources of the
PSSCH that they shall decode in the time domain Timing advance
[0129] Devices interested in receiving D2D/V2V services blindly
scan the whole PSCCH pool to search if a SCI format matching their
group identifier can be detected. On the transmitting device side,
resources to transmit the SCI format information shall be selected
within the PSCCH pool.
[0130] There are two types of resource pools such as reception
resource pools (Rx RPs) and transmission resource pools (Tx RPs).
These are either signaled by the eNodeB for in-coverage case or a
pre-configured value is used for the out-of-coverage case. Within a
cell, there may be more Rx RPs than Tx RPs to enable reception from
adjacent cells or from out-of-coverage UEs.
[0131] Two modes of resource allocation have been defined for SL
communication such as a Mode 1 (e.g., scheduled resource
allocation) and a Mode 2 (e.g., autonomous resource selection). In
one example, in mode 1, access to the SL resources is driven by the
eNodeB. The UE needs to be connected to transmit data. In such
example, the UE wishing to use direct communication feature sends
an indication to the network. The UE may be assigned a temporary
identifier SL-RNTI (Sidelink Radio Network Temporary Identifier).
This identifier may be used by the eNodeB to schedule the future
D2D/V2V transmission
[0132] When the UE has some data to transmit in D2D/V2V mode, the
UE sends an SL buffer status report (SL-BSR) to the eNodeB which
gives an indication on the amount of data to be transmitted in
D2D/V2V mode. Based on this information, the eNodeB sends to the UE
the allocation on both PSCCH and PSSCH for its D2D/V2V
transmission. The allocation information is sent over the PDCCH by
sending a DCI Format 5, scrambled by the SL-RNTI. The information
contained in DCI format 5 is detailed in TABLE 2. A large part of
the DCI Format 5 information is directly reflected in the content
of the SCI format 0. Based on the information received in the DCI
format 5, the D2D transmitting devices sends the SCI format 0 over
the resources within the PSCCH pool allocated by the eNodeB,
followed by the data over the resources allocated by the eNodeB for
PSSCH transmission.
TABLE-US-00002 TABLE 2 Parameter Usage Resource for PSCCH Provides
the information of the transmitting UE of the resource to be used
for SCI format 0 transmissions within the PSCCH pool. TPC command
If this bit is not set, the transmitting UE is allowed to transmit
D2D signals at maximum power. Otherwise, it shall comply with power
control rules based on open loop. Resource block give to the
receiving devices the information assignment and hopping of the
resources of the PSSCH that they shall resource allocation decode
in the frequency domain Frequency hopping flag Time resource
pattern give to the receiving devices the information (T-RPT) of
the resources of the PSSCH that they shall decode in the time
domain
[0133] In mode 1, there is no pre-allocated or reserved resource
for PSSCH, but the resource is assigned "on-demand" by the eNodeB.
In addition, since the eNodeB is responsible to give access to the
resources within the PSCCH pool, resource collision on the PSCCH
transmission can be avoided.
[0134] In mode 2, the UE transmitting D2D/V2V data does not need to
be connected to the eNodeB. The UE selects autonomously and
randomly the resources within the PSCCH pool to transmit the SA
using SCI Format 0. In addition to the PSCCH pool, there is also a
PSSCH pool which defines reserved resources for PSSCH transmission.
It is defined in a similar way as the PSCCH pool (PRBStart, PRBend,
PRBNum in the frequency domain and a sub-frame bitmap in the time
domain which is repeated up to the next PSCCH occurrence). The SCI
Format 0 designates the portion of the pool that is used for D2D
transmission. Since the transmitting UE is not necessarily
connected to the eNodeB, the timing advance information may be not
known and the corresponding parameter in the SCI Format 0 shall be
set to 0.
[0135] With D2D mode 2 communications, a UE autonomously selects
resources from the SA resource pool to transmit its control
information and from the data resource pool to transmit data. Since
there is no centralized controller in the mode 2, each transmitting
UE can select resources with equal probability from the resource
pools for SA and/or data transmission. Thus, there may be more than
one UE who may select the same resources (e.g., collision
happens).
[0136] When the number of transmitting UEs is beyond 2 or 3 times
the number of resources, the average collision probability can be
over 90% using existing D2D techniques in LTE specification.
Resource collision for V2V is a more severe problem than for Rel-12
D2D since the UE density is higher than a D2D public safety
deployment, especially for urban scenarios. Furthermore, a high
level of collision increases latency which makes it difficult to
meet 100 msec latency requirement for channel assignment message
(CAM) messages and 20 msec requirement for event-triggered
messages.
[0137] There is a requirement for V2X communication that the
E-UTRA(N) (e.g., eNB) may be able to support a high density of UEs
supporting V2X Service. Thus, collision avoidance measures may need
to be considered to support high density of vehicles. Furthermore,
V2X services may operate in shared spectrum such as 5.9 GHz and may
need to co-exist with other technologies. Dedicated short range
communications (DSRC) is a short to medium range communications
service using 5.9 GHz that supports both public safety and private
operations in roadside to vehicle and vehicle to vehicle
communication environments. The DSRC is meant to be a complement to
cellular communications by providing very high data transfer rates
in circumstances where minimizing latency in the communication link
and isolating relatively small communication zones are important.
The DSRC supports seven 10 MHz channels in the 5.85 to 5.925 GHz
frequency bands. At the physical layer, IEEE 802.11p standard based
on Wi-Fi is adopted for communication in this frequency band.
[0138] Energy sensing is the method used for DRSC using IEEE
802.11p. Listen-before-talk (LBT) is also recently supported in
3GPP specification for a license assisted access (LAA). LBT in
Wi-Fi systems works by sensing energy in the time domain and the
resources are completely scheduled in the time and frequency
domain. However, LBT for V2X presents challenges since users can be
scheduled in the frequency domain, making time domain sensing not
valid to sense if a UE is present or not.
[0139] Further the resources in time may not be completely used
since V2V may share spectrum with UL, and one may mistake UL
transmission for V2V transmission if only time-domain based energy
detect is used. There are multiple techniques for V2V to identify
possible collision such as energy detection or reading other UE's
PSCCH (SA scan).
[0140] A semi-persistent scheduling (SPS) is available for DL/UL
communication in LTE, primarily to support voice. Since the PDCCH
is limited size (generally, 3 OFDM symbols), there is a limit as to
how many DCIs can be carried in a subframe. This can in-turn limits
the number of UEs which can receive an allocation for that subframe
when using dynamic scheduling (a 1:1 PDCCH-to-PxSCH method).
[0141] With SPS, the UE is pre-configured by the eNB with an
SPS-RNTI (allocation ID) and a periodicity. Once pre-configured, if
the UE were to receive an allocation (DL/UL) using the SPS-RNTI
(instead of the typical C-RNTI), then this one allocation would
repeat according to the pre-configured periodicity. During SPS,
certain parameters remain fixed for each allocation, for example RB
assignments, modulation and coding scheme, etc. If the radio link
conditions change, a new allocation may have to be sent
(PDCCH).
[0142] SPS can be configured and/or re-configured by RRC at any
time using SPS-Config. This SPS-Config includes the configuration
for semiPersistSchedC-RNTI (sps-CRNTI), sps-ConfigDL and
sps-ConfigUL. SPS can be configured only in the uplink
(sps-ConfigUL), or in the downlink (sps-ConfigDL) or in both
directions. Configuration of SPS does not mean that the UE can
start using SPS grants/assignments.
[0143] The eNB may explicitly activate SPS, in order for the UE to
use SPS grants and/or assignments. Also, to avoid wasting resources
when a data transfer is completed, there are several mechanisms for
deactivating SPS (explicit, inactivity timer, etc.). When
configuring SPS in any direction either UL or DL, SPS C-RNTI is
mandatorily provided by the eNB. Soon after the UE is configured
with SPS C-RNTI, the UE is configured by higher layers to decode
PDCCH with CRC scrambled by the SPS C-RNTI. A UE may monitor PDCCH
with CRC scrambled by the SPS C-RNTI in every subframe as the eNB
can activate/re-activate/release SPS at any time using downlink
control information (DCI).
[0144] In some embodiments, for an SL transmission mode 1 and PSCCH
period i, the UE transmit power P.sub.PSSCH for PSSCH transmission
is given by P.sub.SSCH=p.sub.CMAX,PSSCH if the TPC command field in
configured SL grant for PSCCH period i is set to 0. In some
embodiments, for an SL transmission mode 1 and PSCCH period i, the
UE transmit power P.sub.PSSCH for PSSCH transmission is given by
P.sub.PSSCH=min{P.sub.CMAX,PSSCH, 10
log.sub.10(M.sub.PSSCH)+P.sub.O.sub._.sub.PSSCH,1+.alpha..sub.PSSCH,1PL}
[dBm] if the TPC command field in configured SL grant for PSCCH
period i is set to 1. In such embodiments, P.sub.CMAX,PSSCH is the
maximum transmit power and PSSCH is the bandwidth of the PSSCH
resource assignment expressed in number of resource blocks and
PL=PL.sub.c where PL.sub.c is the path loss.
P.sub.O.sub._.sub.PSSCH,1 and .alpha..sub.PSSCH,1 are provided by
higher layer parameters p0-r12 and alpha-r12, respectively and that
are associated with the corresponding PSSCH resource
configuration.
[0145] For an SL transmission mode 2, the UE transmit power
P.sub.PSSCH for PSSCH transmission is given by
P.sub.PSSCH=min{P.sub.CMAX,PSSCH,10
log.sub.10(M.sub.PSSCH)+P.sub.O.sub._.sub.PSSCH,2+.alpha..sub.PSSCH,2PL}
[dBm]
where, P.sub.O.sub._.sub.PSSCH,2 and .alpha..sub.PSSCH,2 are
provided by higher layer parameter p0-r12 and alpha-r12,
respectively and that are associated with the corresponding PSSCH
resource configuration.
[0146] In some embodiments, for a SL transmission mode 1 and PSCCH
period i, the UE transmit power P.sub.PSCCH for PSCCH transmission
is given by P.sub.PSCCH=p.sub.CMAX,PSCCH if the TPC command field
in the configured SL grant for PSCCH period i is set to 0. In some
embodiments, for a SL transmission mode 1 and PSCCH period i, the
UE transmit power P.sub.PSCCH for PSCCH transmission is given
by
P.sub.PSSCH=min{P.sub.CMAX,PSSCH,10
log.sub.10(M.sub.PSSCH)+P.sub.O.sub._.sub.PSSCH,1+.alpha..sub.PSSCH,1PL}
[dBm]
where if the TPC command field in the configured SL grant for PSCCH
period i is set to 1, P.sub.CMAX,PSCCH is the maximum transmit
power for the control channel and M.sub.PSCCH=1 and PL=PL.sub.c is
the path loss. P.sub.O.sub._.sub.PSCCH,1 and .alpha..sub.PSCCH,1
are provided by higher layer parameters p0-r12 and alpha-r12,
respectively and are associated with the corresponding PSCCH
resource configuration.
[0147] For SL transmission mode 2, the UE transmit power P PSCCH
for PSCCH transmission is given by
P.sub.PSSCH=min{P.sub.CMAX,PSSCH,10
log.sub.10(M.sub.PSSCH)+P.sub.O.sub._.sub.PSSCH,2+.alpha..sub.PSSCH,2PL}
[dBm]
where P.sub.CMAX,PSCCH is the P.sub.CMAX,c configured by higher
layers and M.sub.PSCCH=1. P.sub.O.sub._.sub.PSCCH,2 and
.alpha..sub.PSCCH,2 are provided by higher layer parameters p0-r12
and alpha-r12, respectively and are associated with the
corresponding PSCCH resource configuration.
[0148] There is a need to enhance the collision avoidance mechanism
for V2V communications for some reasons. In one example, there is a
requirement for V2X communication that for particular usage (i.e.,
pre-crash sensing) only, the E-UTRA(N) should be capable of
transferring V2X messages between two UEs supporting V2V Service
with a maximum latency of 20 msec. There is also a requirement that
the 3GPP network may be able to provide means to prioritize
transmission of V2X messages according to their type (e.g. safety
vs. non-safety). These stringent requirements for safety messages
may be considered for enhancing the collision avoidance
mechanism.
[0149] In another example, there is a requirement for V2X
communication that the E-UTRA(N) may be able to support a high
density of UEs supporting V2X Service. When the number of
transmitting UEs in Mode 2 operation is beyond 2 or 3 times the
number of resources, the average resource collision probability can
be over 90% using existing D2D techniques. Hence, reducing
collisions in Mode 2 operation is important for V2V communication.
In D2D, collision avoidance was performed by randomization of
resource selection. However, this is not sufficient for V2V and
sensing mechanisms need to be introduced.
[0150] In existing D2D techniques, the main purpose was to reduce
the D2D interference on the cellular link. It can be re-used for
LTE-V2X if V2V transmission using shared carrier with cellular
transmission. However, even if a dedicated carrier is used for V2V,
power control may still be necessary for V2X to mitigate
interference and minimize collisions. When sensing is performed
based on energy, transmit power of other UEs may also need to be
accounted for in the sensing procedure.
[0151] The frequency band for V2V communication can be shared
between cellular-based V2V and DSRC (for example, at 5.9 GHz). In
this case, it is important to detect and co-exist with existing
DSRC transmissions to avoid collisions between DSRC and
cellular-based V2V communication.
[0152] In one embodiment, the scheduling assignment (SA) pool
resources are scanned first before transmission to determine which
of the SA and data pool resources are currently being used. The SA
scan provides the information about the SA and data pool resources
used by the UE, including the time and frequency resources and the
persistence time for which this allocation (allocation period) (if
semi-persistent) is valid. If the SA scan of the other UE
transmissions is decoded successfully, those SA and data resources
are avoided for use of transmission until the allocation period
expires.
[0153] In one embodiment, the resource pools are separated for mode
1 and mode 2 operation such that there is no overlap in resources.
This can be one method to limit resource collision. In this case,
at least the devices operating in mode 1 can be efficiently
scheduled by the eNodeB and the collision is limited to the pool
supporting mode 2 devices. This assumes sufficient resources exist
to support separate pools for mode 1 and mode 2 devices.
Furthermore, one or more reserved pools are defined separately for
event triggered messages due to the requirements for higher
reliability and lower latency, where more care is taken to minimize
collisions by providing more resources or having multiple such
pools, for example.
[0154] FIG. 7 illustrates an example resource pool for several
modes and traffic types 700 according to embodiments of the present
disclosure. An embodiment of the resource pool for several modes
and traffic types 700 in FIG. 7 is for illustration only. Other
embodiments may be used without departing from the scope of the
present disclosure.
[0155] As shown in FIG. 7, the resource pool comprises a mode 1
pool(s) 705, a mode 2 pool(s) 710, and a reserved pool(s) 715. More
specifically, FIG. 7 represents an example of the resource pools
being categorized for mode 1, mode 2 and event triggered traffic
operation, each of which has separate resources.
[0156] In one embodiment, the resource pools could be transmission
pools or reception pools. A common reception pool could also be
utilized assuming the same message formats are utilized for both
mode 1 and mode 2.
[0157] In one embodiment, a mode 2 operation is performed under
network assistance. The eNodeB may configure certain vehicles in
the network to operate under mode 2 if mode 1 resources are not
available. Furthermore, for vehicles that have just entered the
cell from neighboring cells, mode 2 autonomous allocations may be
used until the network provides a mode 1 configuration for the
device.
[0158] In such cases, it may be beneficial to support mode 2
operations with network assistance to minimize collisions.
Semi-persistent scheduling for CAM messages not only minimizes
control overhead but also minimizes collisions for control. The UE
operating under Mode 2 can request the eNodeB to provide a list of
known resources (SA and/or data) being used. The resource list
transmission can also be initiated by the eNodeB, as an alternative
option. Furthermore, instead of sending a list of known resources
that are used, a list of unused resources could be transmitted by
the eNodeB.
[0159] The UE filters the potentially available resources based on
this list. The UE can further scan the resources of other UEs in
the resource pool for additional filtering. The UE makes a decision
for the resource selection based on the result of the scan and the
list provided by the eNodeB. Thus the list of resource choices for
transmission is restricted in this approach to reduce the collision
probability. The UE can also report the UE's used resources to the
eNodeB. If none of the identified resources are available, the UE
can request the eNodeB for any updated list and does not transmit
anything until it has found a suitable re-assignment after a
re-scan. The eNodeB can also request the UE to provide a scan
report for all resources, which it can use for informing other Mode
2 devices under network assistance and to guide MCS and transmit
power setting for the UE.
[0160] FIG. 8 illustrates an example procedure for a mode 2
operation with network assistance according to embodiments of the
present disclosure. An embodiment of the procedure for the mode 2
operation with network assistance shown in FIG. 8 is for
illustration only. Other embodiments may be used without departing
from the scope of the present disclosure. As shown FIG. 8, the
network 800 comprises a UE 801, a plurality of UEs 802, and an
E-UTRAN (e.g., eNB) 803.
[0161] The UE 801 in Mode 2 requests a resource list from the
eNodeB 803. The eNodeB 503 provides a list of known resources. The
UE 801 filters its choices of transmission based on this list. The
UE 801 may additionally scan the resource transmissions from
neighboring UEs 802 to filter its choices further. The UE 801 then
randomly selects resources for its operation out of the remaining
options. The UE 801 may then inform the eNodeB 803 of the UE 801's
selected choice of resources for helping it inform other Mode 2
devices requesting network assistance for collision avoidance.
[0162] For such safety or event triggered messages, reading
resources of other UEs or requesting a resource utilization list
from the eNodeB is not an option. Ideally, a separate pool is to be
used for safety messages, which is designed with enough
provisioning to minimize collisions. In this case, reading the SA
does not help as there will not be any further transmission soon
since the event has already occurred. Also, the UE cannot wait to
request a list from the eNodeB and take action in this case. The UE
sends these event triggered messages at maximum power at lowest MCS
in this case to guarantee reception (coverage). The resources of
the transmissions in the SA can be randomized and it can be
repeated multiple times as well to minimize collision
(interference). It is assumed not all UEs will send an emergency
message at the same time--i.e. such messages are not relayed over
multiple hops. This reserved pool can made common to all UEs for
transmitting and receiving emergency messages.
[0163] In one embodiment, a Mode 2 operation is supported without
network support. For mode 2 operation without network support, the
UE has to make autonomous decisions for collision avoidance. In
this case, UE scans all available resources autonomously before
transmissions and picks unused resources to use. For CAM messages,
once a transmission choice is made for the resources, it is kept
semi-persistent. This helps the resource pool allocation be stable
for scanning and resource selection by UEs in mode 2 operation. The
UE can continue to scan the pool during this period and if it sees
a change in the pool (for example, one UE in the pool has stopped
transmitting its allocated resources); the UE can trigger a
re-selection. If the UE is able to identify that no free resources
are available for transmission based on the resource scan, the UE
defers transmission and waits until the end of the transmission
period to evaluate the resources again for any open positions for
transmitting its message.
[0164] FIG. 9 illustrates an example procedure for a mode 2
operation without network assistance 900 according to embodiments
of the present disclosure. An embodiment of the procedures for the
mode 2 operation without network assistance 900 shown in FIG. 9 is
for illustration only. Other embodiments may be used without
departing from the scope of the present disclosure. As shown in
FIG. 9, the procedure 900 comprises a UE 901, a plurality of UEs
902, and an E-UTRAN (e.g., eNB) 903.
[0165] The UE 901 first scans the resource pool for transmissions
from neighboring UEs 902. This resource pool may be pre-configured
by the eNodeB 903 for operation. On determining a set of available
resources, the UE 901 randomly selects resources out of the
available choices and transmits its SA and/or data.
[0166] As discussed in mode 2 operation aforementioned with network
support, the procedure for event triggered messages is different
where sensing the resources of other users is not beneficial. In
this case, the UE autonomously selects resources from a separate
pool randomly and the UE can be repeated multiple times as well to
minimize collision.
[0167] In one embodiment, the MCS and transmit power is adjusted
for collision avoidance. In mode 2 operation with network
assistance, the eNodeB can set the MCS and transmit power based on
its view of the network to minimize collision avoidance. In mode 2
operation without network assistance, when a pool is scanned, if
there is no existing UE in the pool, the UE assumes there are no
resources used by any other UEs.
[0168] In this case, the UE can transmit at a high power (as
allowed by the power control setting for transmission) and lowest
MCS (open loop). If the transmit power is already at maximum level,
the MCS can be further decreased in this case. If there are
existing UEs in the pool, the UE can derive a path loss estimate to
each UE based on the received RSRP/RSSI measurements from the users
in the pool. This can be averaged and used to set the transmit
power.
[0169] FIG. 10 illustrates an example transmission power adaptation
1000 based on traffic conditions according to embodiments of the
present disclosure. An embodiment of the transmission power
adaptation 1000 based on traffic conditions in FIG. 10 is for
illustration only. Other embodiments may be used without departing
from the scope of the present disclosure.
[0170] As shown in FIG. 10, the transmission power adaptation 1000
comprises a UE 1001a, a UE 1002a in a high transmission power, and
a plurality of UEs 1002a and a plurality of UEs 1002b. It would be
beneficial to adapt the transmission power based on traffic
conditions as shown in FIG. 10.
[0171] When the traffic density is higher, the transmission range
may be reduced to minimize collisions and have greater re-use of
resource pools. As shown in FIG. 10, when the distance between the
transmitting UE 1001 and receiving UE(s) 1002 is large, the
transmit power can be high to maintain coverage. However, when the
distance is small, the transmit power may be reduced to minimize
collisions. The traffic conditions can be inferred in multiple
ways. In mode 1 operation, for example, the eNodeB can have
knowledge of the traffic condition in a given area and indicates to
the transmitting UE to reduce the transmit power in case of
significant traffic. In mode 2 operation, the transmitting UE can
scan the SA of other UEs and estimate the approximate path loss
based on RSRP/RSSI measurements. It can accordingly adjust its
transmission power based on an average of the estimated path loss
from multiple UEs observed from the scan.
[0172] The mechanism to calculate RSRP for every UE data
transmission is not available for an SL. To estimate the path loss
from each transmitting UE, one cannot use the SL RSRP (S-RSRP)
based on the PSBCH since as the received PSBCH may be a combined
signal from multiple UEs and may not be uniquely identified within
a cell. Other reference signals such as DMRS from the SA cannot be
used as well since those reference signals may be transmitted at
variable power.
[0173] In one embodiment, a power setting information is
communicated in the SA to indicate the transmit power used. On
decoding the SA, one can figure out the reference transmit power
used--from which the path loss can be estimated for power
adjustment. This power setting can be indicated by using a few bits
in the SCI format, for example. For example, 5 bits in the SCI
format sent in the SA can be used to indicate the power setting,
where `00000` can represent muting and `11111` can represent max
transmit power that is configured by the eNodeB.
[0174] The power setting can also be indicated as an absolute value
indication (e.g. dBm) or as an offset from a fixed value. This
fixed value can be configured by higher layers or can be indicated
by the PSBCH. It may not be accurate to use all SA transmissions
for RSRP but use only those who are observed in the current SA pool
of the transmitting UE. Based on these measurements from multiple
UEs observed from the SA scan, an average SA-RSRP can be calculated
and the transmit power can be computed as a backoff from the
maximum transmission power. The minimum SA-RSRP can also be used if
it is desired to communicate with every UE which was observed from
the scan. If there are no UEs reported from the SA scan, the
maximum transmission power can be used.
[0175] In one embodiment, the path loss for the power adjustment is
achieved based on the transmission of a known reference signal with
a fixed transmit power. A new reference signal with a fixed
transmit power can be used for RSRP measurement on a UE-specific
basis for SL, which can be denoted as SA-RSRP. The new reference
signal can be sent in a sub-frame after every PSBCH
transmission.
[0176] Since SL and V2V can share the same resources with uplink,
there may be collisions in mode 1 operation if the V2V UE cannot
distinguish which resources are to be used for SL vs. V2V. The
sub-frame bitmap used in the current resource assignments in D2D
Rel-12 currently only distinguishes PC5 and UL resources.
[0177] In one embodiment, a separate bitmap (V2V subframe bitmap)
is used to indicate which resources are to be used for V2V
communication to distinguish from the SL D2D bitmap. The eNodeB
communicates both V2V and D2D bitmaps to the UE in its allocation
using the DCI format. As an alternative approach, the current 1-bit
bitmap for D2D can carry an additional bit to distinguish from V2V
communication. TABLE 3 shows an example mapping between the
subframe bitmap and the assignments for uplink, sidelink (D2D) and
sidelink (V2V).
TABLE-US-00003 TABLE 3 Bitmap assignment Communication 00 Uplink 01
Sidelink (PC5) 10 Sidelink (V2V) 11 reserved
[0178] FIG. 11 illustrates an example device-to-device (D2D) and
vehicle-to-vehicle (V2V) subframes 1100 according to embodiments of
the present disclosure. An embodiment of the D2D and V2V subframes
1100 shown in FIG. 11 is for illustration only. Other embodiments
may be used without departing from the scope of the present
disclosure.
[0179] As shown in FIG. 11, subframes 1100 comprise D2D and V2V
subframes 1101 and 1103 and a set of joint subframe bitmap 1102.
The option of D2D subframe 1101 shows the use of separate bitmaps
for V2V and D2D subframes, where 0 is used to determine UL and 1 is
used to determine V2V and D2D, depending on the bitmap. In option
1102, the bitmaps are put together and used according to TABLE
3.
[0180] In some embodiments of sensing based on SA scan (PSCCH
decoding) of other UEs, the locations of the SA transmissions are
assumed to be known and decodable by all UEs (e.g., blind decoding
could be used, if required). If the SA of another UE is decoded
successfully, the transmitting UE has guaranteed knowledge of
future SA and data transmissions and resource utilization of that
UE. Since there is a restriction on number of PSCCHs in a subframe,
the complexity of this decoding is not significant. Successful
decoding of the SA of all interfering UEs may be difficult under
high interference (low SINR), which can occur in dense traffic
scenarios.
[0181] In some embodiments of energy based sensing, the energy
sensing is performed in the frequency domain. An energy threshold
is used to identify available resources for transmission. The
assumption for energy based sensing is that the resource occupancy
does not change for future transmissions i.e. resources that are
observed as idle are likely to remain idle in the future and the
next transmissions from other UEs will use the same resources used
previously. The result may not be highly reliable esp. at low SNR
and high mobility scenarios, but may provide acceptable values of
probabilities of misdetection and false alarm, in certain
conditions.
[0182] In such embodiments, aforementioned sensing techniques are
complementary and need not be used on an exclusive manner.
[0183] FIG. 12 illustrates an example collision avoidance method
1200 according to embodiments of the present disclosure. An
embodiment of the collision avoidance method 1200 shown in FIG. 12
is for illustration only. Other embodiments may be used without
departing from the scope of the present disclosure. For example,
the collision avoidance method 1200 may be performed by a UE, such
as for example, the UE 116 in FIG. 3.
[0184] As shown in FIG. 12, the collision avoidance method 1200
begins at step 1201. At step 1201, the UE performs sensing-I
operation including decoded SA of other UEs. The UE performs step
1202, at step 1202, the UE performs sensing-II operation including
detecting energy across resources. At step 1203, the UE performs
selection-I excluding resources based on sensing. At step 1204, the
UE performs selectin-II selecting parameters for transmission.
Finally, the UE transmits on selected resources with selected
parameters at step 1206. At step 1207, if the resource is
reselected, the UE performs step 1201. If the resource is not
selected at step 1207, the UE performs step 1206.
[0185] More specifically, at step 1201, the UE first attempts to
decode the SA (PSCCH) of other UEs to figure out the resources that
may be used in future transmissions by other UEs. However, it is
possible that in certain scenarios, such as high interference, the
SA may not be decodable. These cases can be indicated by reception
of high energy in the SA resources but unsuccessful decoding of the
SA. In such cases, the UE can perform energy sensing across all
resources in step 902 to investigate potential SA and data
transmissions. Thus, both SA decoding and energy measurement can be
supported for sensing in UE autonomous resource selection.
[0186] Based on the sensing results from SA decoding and/or energy
sensing, the UE makes a decision in step 1203 on the resources that
need to be excluded in the transmission. Thus, a UE identifies the
resources that will be occupied and/or collided by the other UEs
and avoids a colliding resource allocation for its transmission.
Based on the remaining resources available for transmission, the UE
then selects the resources to be used for transmission in step
1204.
[0187] The UE then selects the transmission parameters such as
transmit power, MCS, semi-persistent transmission related
parameters such as next transmission interval etc. in step 1205 and
transmits in the selected resources with the selected transmission
parameters in step 1206. The UE finally makes a decision whether to
continue this transmission on the selected resources or re-start
the process for a new transmission in step 1207.
[0188] SA transmissions from each UE may use a limited number of
PRBs. To uniquely identify SA power, high resolution sensing (e.g.,
accurate energy measurement at every PRB) may be performed. Since
SA and data can be multiplexed in the same subframe, the SA
transmission power can be different among different UEs, and UEs in
proximity of the transmitting UE can have lower transmit power than
UEs that are further away which need not communicate to the
transmitting UE. Data transmissions from each UE may use a group of
PRBs (e.g., RB groups) and hence can use a coarser resolution for
sensing. However, this comes at an expense of losing the
flexibility of fine resource allocation in the frequency
domain.
[0189] To adjust for transmit power variations between different
UEs, an indication of the transmit power for SA and/or data (either
total power or per RB group) in the SCI transmissions for energy
sensing may be performed, for example, a field in the SCI is used
to indicate the transmit power. The energy sensing results are then
adjusted based on the transmit power offset per RB group. Note that
only relative transmit power differences are needed for the
adjustment.
[0190] In one embodiment, the transmit power for the SA is fixed
since the transmit power may need to have a long communication
range, irrespective of the data transmission range. Hence, only the
data transmission power needs to be indicated in this case. When a
transport block (TB) is fragmented and transmitted over multiple
sub-frames and RB groups, it is assumed that the transmit power per
RB group is the same. Hence, reporting the transmit power per RB
group in SCI may be sufficient in this case.
[0191] Assuming the energy sensing results for each RB group are
G(k) and let P(k) is the transmit power assigned per RB group
obtained from decoding the SA from different UEs, the RBs, where no
UE transmissions were identified, are assigned to a constant value
such as the maximum transmit power per RB group. Then, the
normalized energy sensing results S(k)=G(k)-P(k), where S(k), G(k)
and P(k) are in dB scale.
[0192] FIG. 13 illustrates an example adjustment of power sensing
results 1300 with transmit power according to embodiments of the
present disclosure. An embodiment of the adjustment of power
sensing results 1300 with transmits power shown in FIG. 13 is for
illustration only. Other embodiments may be used without departing
from the scope of the present disclosure. As shown in FIG. 13, the
adjustment of power sensing results 1300 comprises an energy
sensing result 1305, unknown TX power and power from SA 1310, and
adjusted energy sensing results 1315.
[0193] The raw energy sensing results (all plots are shown
normalized) are adjusted based on the transmit power used based on
the decoding of the SA.
[0194] FIG. 14 illustrates an example procedure for sensing based
on scheduling assignment (SA) decoding and energy measurement
according to embodiments of the present disclosure. An embodiment
of the method for sensing based on SA decoding and energy
measurement shown in FIG. 14 is for illustration only. Other
embodiments may be used without departing from the scope of the
present disclosure.
[0195] As shown in FIG. 14, the procedure for sensing comprises
identifying and ordering potential RB groups for resource
reselection 1405, unused RB groups based on SA decoding 1410,
current and low priority RB groups in use 1415, RB groups excluded
for resource reselection 1420, and BR groups available for resource
reselection 1425.
[0196] A list of potential data resources in RB groups for resource
reselection 1405 is identified for resource selection, where each
RB group is the minimum number of RBs used for data transmission,
for example, all resources are considered available at the
beginning. The transmitting UE performs blind decoding on SA
resources of other UEs to investigate which of the potential RB
groups are in use. The RB groups indicated by successful decodes of
PSCCH of other UEs are first prioritized.
[0197] Any resources indicating being used by UEs transmitting
higher priority traffic may be first excluded for transmission by
low priority users. This implies that packets with different
priorities can be transmitted on the same resource pool. The
priority indication in the SCI can be determined based on different
scrambling, for example, for low and high priority traffic or can
be explicitly indicated. Energy based sensing is then performed on
the remaining potential RB groups and the RB groups are sorted
again based on the energy measurement.
[0198] UE compares the energy on the currently selected resource
with the energy of the resources in the subset. If the energy in a
RB group exceeds a threshold m, those RBs are identified as
unavailable. The transmitting UE can then select resources starting
from the first RB group identified as available in the sorted list
for transmission. Thus, the UE measures and ranks the remaining
PSSCH resources based on total received energy and selects a
subset. The threshold m can be statically configured by the eNB for
operation or can be computed dynamically based on a function of the
energy measurement across RB groups.
[0199] Since the resources available after excluding occupied
resources may be fragmented, a transmission mode for PSSCH that
allows multi-cluster transmissions may be considered, where the
PSSCH resources can be distributed among the frequency resources in
multiple clusters (i.e. non-contiguous). This can allow better
utilization of resources in situations, where contiguous resource
allocation is not available for transmission. It is possible that
limits be placed on the number of clusters to minimize maximum
power reduction (MPR) issues.
[0200] Once available resources are identified and if the amount of
resources needed is less than those available, multiple methods are
available for resource re-selection. In one example, if all
resources identified have equal weight for reselection, the
resources are chosen randomly among available resources. In another
example, if resources identified have some priority for
reselection, the resources are chosen which have least interference
for transmission. In yet another example, if the amount of
resources available for transmission in a single sub-frame is not
sufficient, the transmitting UE can create multiple TBs across
multiple sub-frames that make use of available resources.
[0201] Once available resources are identified and if the amount of
resources needed is less than those available in a contiguous
manner, multiple methods are available for resource re-selection.
In one example, if all resources identified have equal weight for
reselection, the resources are chosen randomly among available
resources. In yet another example, if all resources identified have
equal weight for reselection, the resources are chosen to be
contiguous to an existing transmission (if present) to minimize
resource fragmentation, else resources are selected from one end of
the resource pool in frequency. In yet another example, if
resources identified have some priority for reselection, the
resources are chosen among the contiguous resources which have
least interference for transmission. In yet another example, if the
amount of contiguous resources available for transmission in a
single sub-frame is not sufficient, the transmitting UE can create
multiple TBs across multiple sub-frames that make use of contiguous
available resources.
[0202] In case of sensing periodic traffic with 100 ms or larger
period, it is important to perform sensing for multiple
transmission durations before triggering resource selection. In
case of sensing higher priority traffic, resource reselection may
be performed immediately, possibly within for example, 4 subframes
of sensing higher priority traffic. Based on these two conditions,
the UE at least senses in a window between subframe n-a and
subframe n-b to trigger resource selection/reselection, where n is
the current subframe where resource selection and/or reselection is
triggered. In one example, the parameters a=1000 and b=4 can be
used. In another example, a=1000 and b=0 can be used.
[0203] All UEs in a given resource pool may use the same sensing
window period for the UE's transmissions. This implies that the
values `a` and `b` are common for V2V UEs and are fixed.
Alternately, the parameters a and b can be configured by the eNB
(e.g., not fixed). This could be based on the geo location, speed
or UE synchronization source. Once the resource reselection is
triggered, the UE selects time-frequency resources and transmission
parameters for PSSCH transmission. The UE then transmits SA (PSCCH)
based on the next available opportunity in subframe n+c to transmit
the SA, where c is UE dependent based on its resource availability
for transmission of the SA.
[0204] The PSSCH is then transmitted in the same or following
subframes in subframe n+d. d may be limited in range between
subframes d.sub.min and d.sub.max, where d.sub.min=c represents
same sub-frame transmission and d.sub.max=N+c represents
transmission within the end of the transmission period (N=100 ms,
for e.g.) for PSSCH. The SA/PSCCH also indicates the next potential
transmission time at n+e, where 1000+c>e>d.sub.max.
[0205] The maximum values of c and d can be restricted further
based on priority. For example, c, d.ltoreq.100 for low priority
traffic while c, d.ltoreq.20 for high priority traffic. e could be
offset from d in a multiple of period P (e.g., 100 ms).
e=k*P.sub.min+d, where k can be an integer in range {0, . . . , 10}
i.e. 0.ltoreq.k.ltoreq.10, and P.sub.min=100, for example, is the
minimum periodicity interval. k=0 implies there is no future
transmission and k=10 represents maximum periodicity (1 second).
This indication of the offset (e-d) could be done based on a
transmission periodicity field or a next transmission time or
inter-TB duration field set in the SCI.
[0206] In one embodiment, if this next transmission time field in
the SCI is set to 0, it implies that this transmission is not
persistent and this resource is not planned to be used in a future
transmission interval by the UE. The receiving UE for sensing uses
this field to identify the resources being reserved for future
transmissions and avoids those resources in the UE's resource
allocation and selection procedures. The value `e-d` can then be
indicated in the SCI by 4 bits to represent numbers between 0 and
10. Value 0 can indicate no next transmission (e.g., ending current
periodic traffic or aperiodic traffic), Value 1 can indicate next
transmission is at 100 ms, and Value 10 indicates next transmission
is at 1 sec. Values 11-15 can be reserved.
[0207] Receiver UE assumes that the traffic may be semi-persistent
with periodicity indicated by e-d. If the transmitting UE changes
the value indicated in e-d, the receiver UE can re-evaluate and
adjust the UE's resource allocation, if necessary.
[0208] FIG. 15 illustrates an example sensing duration 1500
according to embodiments of the present disclosure. An embodiment
of the sensing duration 1500 shown in FIG. 15 is for illustration
only. Other embodiments may be used without departing from the
scope of the present disclosure. As shown in FIG. 15, the sensing
duration 1500 comprises a sensing duration 1505, an SA 1510, data
1515, and a net transmission 1520. Based on sensing across a
window, a resource availability map can be identified for future
transmissions.
[0209] FIG. 16 illustrates an example sensing results 1600 in
different subframes (SF) according to embodiments of the present
disclosure. An embodiment of the sensing results 1600 in different
SF shown in FIG. 16 is for illustration only. Other embodiments may
be used without departing from the scope of the present
disclosure.
[0210] As shown in FIG. 16, the sensing results 1600 comprises a
group of RBs 1601, resources 1602 and 1603, used resources 1604,
and remaining resources 1605. The group of RBs 1601 is identified
as high priority transmissions, which are excluded from resource
reselection. For resources, identified by SA decoding, the
periodicity can be determined from their SCI transmissions. For
example, the resources 1602 may have periodicity of P1=100 ms,
while the resources 1603 may have a different periodicity of P2=300
ms. In addition, there may be resources 1604 identified as used
based on energy sensing. The remaining resources 1605 are
considered as available based on the sensing results.
[0211] If a sub-frame m is skipped for sensing by a UE, for any
reason, due to the UE's own transmission in that subframe, resource
selection in subframes at m+k*P.sub.min, where k is an integer and
k>0 and P.sub.min=100, may be avoided until a sensing operation
is performed in the future in a sub-frame m+k*P.sub.min, where k is
an integer and k>0. Alternately, this can be expressed in order
to select resources for transmission in a future sub-frame `m`, the
UE may have performed sensing in all of the sub-frames
"m-k*P.sub.min", where k is an integer, 1.ltoreq.k.ltoreq.10, and
P.sub.min=100.
[0212] In some embodiments, the transmitting UE (e.g., vehicle)
adjusts the UE's transmission power based on the resources
utilization observed by sensing of the occupied resources. Transmit
power control in conjunction with sensing can be used in order to
limit the communication range and improve probability of detecting
the SA of other users.
[0213] FIG. 17 illustrates an example a number of SA transmission
1700 according to embodiments of the present disclosure. An
embodiment of the number of SA transmission 1700 shown in FIG. 17
is for illustration only. Other embodiments may be used without
departing from the scope of the present disclosure.
[0214] As shown in FIG. 17, the number of SA transmission 1700
comprises a number of UE SA transmissions 1705 and transmit power
1710. More specifically, FIG. 17 shows an illustrative example of
the number of SA transmissions received as a function of transmit
power for a worst case scenario of a freeway where there is a
traffic jam on both directions and all vehicles have stopped (i.e.
UE speed=0 km/h).
[0215] If there are 6 lanes and the communication range in 320 m
for the freeway case when all cars are transmitting at 23 dBm
transmit power, and the distance between the centers of 2 cars is 4
m in both front/back and side directions, as shown in FIG. 16, up
to 960 cars are supported within communication range of a given
UE.
[0216] If all 960 cars are going to be broadcasting on SL, there
most likely will not be sufficient resources to support all
transmissions with exclusive resources, leading to significant
collisions and making it difficult for decoding SA of other users.
If the transmit power by 30 dB to -7 dBm in this is reduced, the
communication range can be reduced to 10 m, which may be sufficient
for communicating with .about.16 adjacent vehicles as shown in FIG.
4, with a better probability of decoding the SA.
[0217] FIG. 18 illustrates an example sensing based on SA scan and
energy saving 1800 according to embodiments of the present
disclosure. An embodiment of the sensing based on SA scan and
energy saving 1800 shown in FIG. 18 is for illustration only. Other
embodiments may be used without departing from the scope of the
present disclosure.
[0218] As shown in FIG. 18, the sensing based on SA scan and energy
saving 1800 comprises SA and/or data resource blocks 1801-1804 and
resource utilizations 1805-1808. The SA scan indicates the SA
and/or data resource blocks 1801-1804 being utilized. The energy
sensing shows the resource utilization 1805-1808. The resource 1804
from energy scan got missed in energy sensing due to distance
and/or difference between transmit power for SA and data. For
example, the SA was received and indicated use of resource 1804 for
data but resource 1804 did not show up in energy scan since it was
transmitted at much lower power. Also, resource 1806 in energy
sensing got missed in SA scan due to collision or interference on
that resource.
[0219] In one embodiment, the union of SA/data resources indicated
by the SA scan and energy sensing may be excluded for transmission.
In another embodiment, the resources indicated by the SA scan may
be prioritized in the exclusion. In yet another embodiment, the
resources exceeding a certain energy threshold may be prioritized
in the exclusion. In yet another embodiment, the energy scan can
differentiate the resource utilization based on the SA type (e.g.
periodic vs. event-triggered messages). The energy scan for
periodic messages may show a different response when scanned over
time compared to event triggered messages. Resource selection can
then be prioritized based on the type of resource (e.g. avoid
emergency resources compared to periodic traffic).
[0220] FIG. 19 illustrates an example energy scan 1900 on different
periodicities and event trigged traffic according to embodiments of
the present disclosure. An embodiment of the energy scan 1900 on
different periodicities and event trigged traffic shown in FIG. 19
is for illustration only. Other embodiments may be used without
departing from the scope of the present disclosure.
[0221] As shown in FIG. 19, the energy scan 1900 comprises a period
traffic 1901 and event triggered traffic transmission 1902. More
specifically, the periodic traffic 1901 may show up at regular
intervals or multiples of P=100 ms on a resource for example, while
the event triggered traffic transmission 1902 may occur in a short
bursts with potentially higher transmit power to enable low latency
and higher reliability
[0222] If the sensing implies that there is no vehicle UE occupying
any resources, the transmitting UE picks one of the available SA
(PSCCH) and data (PSSCH) resources for transmission of its SA and
data for the next transmission opportunity. It assumes all
resources are available for PSSCH and PSCCH transmission in this
case. It transmits at a baseline allowed power according to power
control rules for PSSCH and PSCCH. For example, in some cases, this
baseline allowed power could be the maximum allowed power for PSSCH
and PSCCH. As increased resource utilization is observed based on
sensing, the transmitting UE excludes those SA and data resources
for the UE's transmissions and lowers the UE's transmit power
dynamically for every transmission. The transmit power can be
dynamically lowered for example, in steps of 3 dB for every
doubling of resources observed in sensing, until the power reaches
the minimum value required to maintain a link. This allows greater
spatial re-use of resources due to power control.
[0223] The dynamic power adjustment for SA and data is done
individually irrespective of whether it is time division
multiplexing (TDM) or frequency division multiplexing (FDM)
multiplexing of SA and data, where the initial transmit power
(assuming no other UE is sensed) is set according to power control
rules for PSSCH and PSCCH.
[0224] FIG. 20 illustrates an example power adjustment based on
sensing results 2000 according to embodiments of the present
disclosure. An embodiment of the power adjustment based on sensing
results 2000 shown in FIG. 20 is for illustration only. Other
embodiments may be used without departing from the scope of the
present disclosure.
[0225] As shown in FIG. 20, the power adjustments comprises of a
data resource block 2001, transmit powers 2002, 2003, 2004, and
occupied resource block 2005. In case 1, the sensing does not show
any UE occupancy. In this case, the transmitting UE picks one of
the available SA and data resource blocks (RBs) 2001 for the UE's
transmission, for example, randomly as indicated in FIG. 20, which
is sent at an initial baseline allowed power set by the power
control rules for PSSCH and PSCCH.
[0226] The resource block 2001 can represent SA and/or data
transmission and the height of the resource block 2001 in FIG. 20
represents the corresponding transmit power. In cases 2, 3, and 4,
as increased resource utilization is observed based on sensing, the
transmitting UE starts lowering the UE's transmit power as shown in
2002, 2003, and 2004, and excludes the occupied resources 2005 for
the UE's transmission, where 2005 represents either SA and/or data
transmission resources. In case 5, there is no resource available
for transmission based on sensing. In this case, the UE does not
transmit and waits for the next opportunity.
[0227] In one embodiment, semi-persistent transmission information
such as the number of future transmissions, the periodicity and the
expiry of the transmission schedule of SA and data is encoded in
the SA transmissions (PSCCH). On decoding the PSCCH of other UEs,
the transmitting UE not only knows the current SA and data resource
utilization of other UEs but also their future transmissions and
the expiry of the schedule. Thus, the transmitting UE can adjust
the UE's resource selection to minimize conflict with future
transmissions of other UEs as well. Thus, exclusion of SA and data
resources can be based on current sensing results as well as
previous sensing results for semi-persistent scheduling
support.
[0228] In some embodiments, the MCS for transmission is also
adapted based on the sensing results. For example, if the resource
utilization is high based on sensing, the UE transmits with lower
MCS for increased reliability.
[0229] It is understood that triggering of resource selection
implies that there are resources that the UE needs since the UE
intends to transmit (i.e. UE transmission buffer is not empty). In
some embodiment, reselection is triggered when a timer or counter
meets an expiration condition or is reset to a value due to
triggering of reselection based on other conditions. It is possible
that when multiple UEs select the same resources and periodicity
based on sensing the same results, the UEs collide at every
transmission. Hence, it is important to allow some variation in the
counters for every UE so that the UEs get a different view of the
network when performing resource reselection. However, it is also
important that the variation be consistent across all UEs.
[0230] In some embodiments, each UE may independently reset or
initialize the resource re-selection counter to a value randomly
chosen within a range of values. The range may be large enough to
allow accurate sensing and small enough to meet latency and not
have significant change in network conditions. In one example, this
range can be integers between [16, 31], which can be implemented
with a 4-bit counter with a fixed offset of 16. The counter
decrements every transmission period P (for example, every P=100
ms). In addition, other ranges such as [5, 15] can also be
considered. The range could also be dependent on the resource pool.
The UE performs reselection when the counter reaches zero or is
reset due to triggering of resource reselection based on other
conditions.
[0231] In some embodiments, resource reselection is triggered by an
upper layer notification. This could be due to change in the
requirements over the existing transmission. Examples of
requirement changes can include change in latency, reliability,
priority, fairness, or QoS requirements.
[0232] In some embodiments, since each transmitting UE can make
independent decisions for V2V, it is important to provide some
measure of fairness for transmissions. Multiple criteria could be
used for defining fairness. In one example of a criteria 1 (e.g.,
in the autonomous resource allocation mode), a UE may provide other
UEs equal opportunities to access the network. In another example
of criteria 2 (e.g., in the autonomous resource allocation mode), a
UE may not use more resources than necessary for its
transmissions.
[0233] A measurement metric is specified to reflect the congestion
level of a PC5 carrier. The network load or congestion level as
observed by a UE can be defined as the percentage of unavailable
data and/or SA resources observed by the UE based on sensing. For
example, percentage=(number of busy resources in T)/(number of
total resources in T), where T is the measuring interval. To meet
criteria 1, congestion control mechanisms such as reducing MCS,
transmit power, muting etc. could be applied with resource
reselection when the network load conditions exceeds a threshold a,
where 0<a<1, where 1 represents 100% full network load.
[0234] The threshold can be set by the eNB during configuration of
Mode 2. The network load conditions may be estimated based on
sensing of SA contents and/or energy based sensing. Thus, this
measurement is available to higher layers in the UE. Furthermore,
when possible, the network load conditions can also be reported to
the eNB via RRC. The eNB can also request a network load
measurement report from the UE, for example, to help select the
transmission path(s) for V2V messages between PC5 and Uu interfaces
based on the PC5/Uu load.
[0235] FIG. 21 illustrates an example resource utilization overload
2100 according to embodiments of the present disclosure. An
embodiment of the example resource utilization overload 2100 shown
in FIG. 21 is for illustration only. Other embodiments may be used
without departing from the scope of the present disclosure.
[0236] As shown in FIG. 21, the resource utilization overload 2100
comprises a resource utilization observed at transmitting UE 2105
and a time axis 2110. More specifically, FIG. 21 shows an exemplary
embodiment of this disclosure where the transmitting UE takes
different actions to support fairness according to the resource
utilization (e.g., load or congestion level) to meet criteria 2.
The transmitting UE always starts transmissions with minimum
resources needed for the required data transmission (e.g. using
highest allowed MCS). It is allowed to then gradually start
utilizing more resources in future transmissions (e.g., reducing
the MCS) to improve reliability as needed as long as the network
load conditions stay below a threshold b, where 0<b.ltoreq.a.
When the network load conditions are between b and a, the resource
utilization of the transmitting UE is not changed. When the network
load exceeds threshold a, the resource utilization by the
transmitting UE may be reduced by applying congestion control
mechanisms.
[0237] In one example, the UE adjusts radio parameters (e.g., max
TX power, number of retransmissions, MCS range, number of PRBs,
etc.) as a function of priority and this measurement. Also, for
example, the resource utilization can be reduced by dropping the
PC5 transmissions as a function of this measurement and/or
priority. The thresholds a and b can be defined as part of RRC
configuration of Mode 2.
[0238] In some embodiments, when the UE is aware of a change in
zone based on its geo-location, the UE may trigger resource
reselection.
[0239] In some embodiments, if the resources identified for
transmission from current UE conflicts with or overlaps with the
resources identified for transmission by another UE, resource
reselection is triggered.
[0240] In some embodiments, from point of a PHY perspective,
priority can coarsely group into two classes for V2V, one which is
low priority and the other which is high priority. The MAC provides
the coarse priority information to the PHY along with the message
to be transmitted in these two classes. In one example, low
priority traffic could be periodic (CAM) messages and an example of
high priority traffic could be aperiodic (DENM) messages. In
another example, the CRC of the PSCCH for these two priority types
are masked and/or scrambled with different radio network temporary
IDs (RNTIs) to distinguish them during sensing by SA decoding.
[0241] Furthermore, the traffic characteristics of high priority
traffic such as aperiodic DENM messages can have increased
repetitions of short periodicities (e.g. .about.1-10 ms) and high
transmit power which can be distinguished via energy sensing. The
detection of a change in traffic priority by sensing and/or SA
decoding process triggers resource reselection.
[0242] In some embodiments, the eNB may request the transmitting UE
to perform resource reselection. This could be based on indication
from transmitting UE of the current load conditions based on
sensing. In such embodiments, the resource reselection can also
include resource pool reconfiguration based on the load conditions
reported to the eNB by the transmitting UE.
[0243] In some embodiments, in mode 2 operation, a given UE can
prioritize its UL transmission over SL and hence, does not transmit
SL. It is possible that in this case, the sensing mechanism by
other UEs may incorrectly identify that the resources are now
available and other UEs may use this resource. However, when the UE
now transmits SL as well in the same resource, it may cause a
collision. Hence, a UE performs resource reselection, when
prioritizing UL transmissions over SL.
[0244] Some vehicles may face poor quality of service (QoS) if
resources are always occupied as shown in case 5 of FIG. 16. In
such cases, some fairness measure needs to be incorporated to
support such cases.
[0245] In one embodiment, if the sensing result for a transmitting
UE indicates that a certain percentage of occupied resources have
been exceeded, the transmitting UE may discontinue the UE's semi
persistent schedule and may follow resource reselection. This may
give other UEs more opportunities to gain access for
transmission.
[0246] In one embodiment, the period of the semi-persistent
transmissions of SA and data of the transmitting UE is dependent on
the number of occupied SA and data resources observed during
sensing.
[0247] FIG. 22 illustrates an example period of a semi-persistent
transmission of SA and data 2200 according to embodiments of the
present disclosure. An embodiment of period of the semi-persistent
transmission of SA and data 2200 shown in FIG. 22 is for
illustration only. Other embodiments may be used without departing
from the scope of the present disclosure.
[0248] As shown in FIG. 22, the period of the semi-persistent
transmission of SA and data 2200 comprises resources excluded based
on sensing 2205 of resource blocks 2201 and resource blocks for
semi-persistent transmission 2210. As the number of occupied
resource blocks 2201 increases from M.sub.1 to M.sub.2, where
M.sub.1<M.sub.2, the period of semi-persistent transmissions
2202 is increased from P.sub.1 to P.sub.2 to allow more
opportunities for other UEs to transmit, where P.sub.1<P.sub.2.
The resource block allocation and MCS are not changed during
semi-persistent transmissions. Resource blocks (e.g., 2201 and
2202) may be either SA and/or data resources. If no UEs are
detected based on sensing, any period up to a maximum period
configuration P.sub.max can be used where
P.sub.1<P.sub.2.ltoreq.P.sub.max. If all resources are fully
utilized, there is no semi-persistent configuration allowed for SA
and/or data transmissions.
[0249] In one embodiment, the number of transmissions in the
semi-persistent transmissions of SA and data of the transmitting UE
is dependent on the number of occupied SA and data resources
observed in sensing.
[0250] FIG. 23 illustrates an example a number of transmission
selection 2300 according to embodiments of the present disclosure.
An embodiment of the number of transmission selection 2300 shown in
FIG. 23 is for illustration only. Other embodiments may be used
without departing from the scope of the present disclosure.
[0251] As shown in FIG. 23, the number of transmission selection
2300 comprises resources excluded based on sensing resource blocks
2301 and RBs 2302 for semi-persistent transmission. As the number
of occupied resource blocks 2301 increases from M.sub.1 to M.sub.2,
where M.sub.1<M.sub.2, the number of transmissions in the
semi-persistent transmission is decreased from N.sub.1 to N.sub.2
while keeping the same transmission period P.sub.1 to allow more
opportunities for other UEs to transmit, where N.sub.1>N.sub.2.
Resource blocks 2001 and 2302 may be either SA and/or data
resources. Combination approaches can also be considered, for
example, increasing the period and decreasing the number of
transmissions simultaneously based on increased resource usage
observed during sensing. After resource selection is triggered, the
next steps involve selecting the appropriate resources to be used
for transmission.
[0252] The procedure for selecting the transmitting resources after
excluding the occupied resources is performed. In one embodiment,
the UE transmission and the UE's transmission rate are decided
based on the number of contiguous resource blocks available after
excluding the occupied resources based on sensing. In one example,
K.sub.min is assumed as the minimum number of resource block groups
(RB groups) needed for transmitting the PSCCH and/or PSSCH. If
PSCCH and PSSCH are transmitted in FDM in a single-cluster (i.e.
contiguous), then K.sub.min is the sum of those resources else the
resource selection is considered individually for PSCCH and PSSCH.
K.sub.min could be based on the highest MCS used for PSSCH
transmission.
[0253] In another example, K.sub.max is assumed as the maximum
number of resource blocks (RBs) needed for transmitting the PSCCH
and/or PSSCH. This configuration can be based on the lowest MCS
used for transmission of PSSCH. Let the number of resource block
groups available for transmission of PSSCH and/or PSCCH based on
the result of sensing be K.
[0254] In some embodiments of PSSCH transmission, if
K<K.sub.min, there is no transmission and the UE waits for the
next opportunity to transmit. In some embodiments of PSSCH
transmission, if K.gtoreq.K.sub.max, the UE selects a rate for
PSSCH utilizing up to K.sub.max resource blocks and can transmit at
the next opportunity. In some embodiments of PSSCH transmission, if
K.sub.min.ltoreq.K.ltoreq.K.sub.max, the UE selects a rate for
PSSCH utilizing up to K resource blocks and can transmit at the
next opportunity.
[0255] The PSCCH transmission is linked with the PSSCH
transmission. The PSCCH resource availability is explored based on
timing derived from a configurable range of values prior to the
desired transmission of the PSSCH. In some embodiments of PSCCH
transmission, if K<K.sub.min, there is no transmission else. In
some embodiments of PSCCH transmission, the PSCCH can be
transmitted in one of the identified SA resources based on sensing
of the SA pool in time resources corresponding to the configurable
range offset in time from the PSSCH resource. The chosen timing
offset for the PSSCH transmission is indicated in the PSCCH.
[0256] If both conditions for PSCCH and PSSCH transmission are
satisfied, the transmission proceeds at the next opportunity. i.e.
PSCCH and PSSCH need to be transmitted jointly and the resource
allocation of PSSCH and the timing offset, if any, is indicated in
the PSCCH.
[0257] In one embodiment, resource selection would be performed to
randomly select K contiguous block groups, if available. In another
embodiment, the resource block groups to be contiguous to an
existing transmission may be selected to maximize number of
contiguous block availability for other UEs. In yet another
embodiment, resource selection would be performed to select the
first K blocks from a sorted list of available resource block
groups.
[0258] FIG. 24 illustrates an example method for selecting PSCCH
resources 2400 according to embodiments of the present disclosure.
An embodiment of the procedure for selecting PSCCH resources 2400
shown in FIG. 24 is for illustration only. Other embodiments may be
used without departing from the scope of the present disclosure.
For example, the method may be performed by the UE 116 in FIG.
3.
[0259] As shown in FIG. 24, the method begins at step 2405. At step
2405, the UE performs sensing. The UE determines whether PSSCH
resources are available at step 2410. If the PSSCH resources are
available at step 2410, the UE performs step 2415. If not, the UE
performs step 2405. At step 2415, the UE selects PSSCH resources
(t1, f1). Subsequently, the UE identifies potential PSCCH resources
(e.g., time) based on configurable range at step 2420.
Subsequently, the UE selects PSCCH resources in time (t2) at step
2425. At step 2430, the UE determines whether the PSCCH resources
are available in frequency (f2). If the PSCCH resources are
available at step 2430, the UE transmits PSCCH (t2, f2) and PSSCH
(t1, f1) at step 2440. If the PSCCH resources are not available at
step 2430, the UE checks all time resources for the PSCCH at step
2435. If the time resources are not available for the PSCCH at step
2435, the UE performs step 2405. If the time resources are not
available for the PSCCH, the UE performs step 2425.
[0260] As shown in FIG. 24, the time and frequency resources (t1,
f1) for PSSCH are first selected based on sensing. Based on the
potential transmission for PSSCH, the time resource options for
PSCCH are first explored based on the range of values configured
for the timing relationship between PSCCH and PSSCH. A particular
choice of PSCCH time and frequency resources (t2, f2) are then
explored for indication of the transmission of the PSSCH resources.
If no suitable PSCCH resource is found, even though PSSCH resources
are available, the transmission is terminated due to lack of
control channel resources.
[0261] FIG. 25 illustrates an example resource selection procedure
2500 according to embodiments of the present disclosure. An
embodiment of the resource selection procedure 2500 shown in FIG.
2500 is for illustration only. Other embodiments may be used
without departing from the scope of the present disclosure.
[0262] As shown in FIG. 25, the resource selection procedures 2500
comprises a resource block 2501, a plurality of transmit powers
2502, 2503, and 2504, and occupied resources 2505. In Case 1, the
sensing does not show any UE occupancy. In this case, the
transmitting UE picks the available SA and data resource blocks
(RBs) 2501 for a transmission at one edge of the total resource
block allocation, which is sent at a baseline power set according
to power control rules for PSSCH and PSCCH. The resource block 2501
can represent SA and/or data transmission and the height of the
resource block 2501 in FIG. 25 represents the corresponding
transmit power. In cases 2, 3, 4, as increased resource utilization
is observed based on sensing, the transmitting UE starts lowering
its transmit power as shown in 2502, 2503, 2504 and excludes the
occupied resources 2505 for its transmission, where 2505 represents
either SA and/or data transmission resources. In these cases, 2502,
2503 and 2504 transmissions are placed to be contiguous to an
existing transmission from other UEs. In case 5, there is no
resource available for transmission based on sensing. In this case,
the UE does not transmit and waits for the next opportunity.
[0263] Energy based sensing can be useful for collision avoidance
with DSRC/IEEE 802.11p. If the spectrum is shared between
cellular-based V2V and DSRC, certain characteristics of the DSRC
transmission can be detected using energy sensing. DSRC
transmissions based on Wi-Fi/IEEE 802.11p are always full-bandwidth
and are packet-based (continuous transmission).
[0264] The symbol duration for IEEE 802.11p is 8 microsecond (usec)
(e.g., compared to 4 usec for regular IEEE 802.11a), but is still
shorter than the cellular-V2V symbol duration. Since IEEE 802.11p
is packet-based (with a minimum of 13 symbols for a packet with no
data), it can be of sufficient length to be detected in the
frequency domain for cellular V2V. The clock period and FFT size
can also be adapted, if needed, for more accurate energy sensing to
specifically match that of DSRC/IEEE 802.11p. For DSRC detection,
other options such as time domain sensing and preamble detection
could also be considered for higher accuracy.
[0265] In one embodiment, energy based sensing is used to identify
a DSRC/IEEE 802.11p transmission, based on sensing of a
full-bandwidth and continuous signal transmission in the DSRC
frequency band. While using a dedicated band for V2V, in mode 1
transmission, the eNodeB can periodically request the UE to do an
energy scan on the DSRC band and report the presence of any DSRC
transmissions. The UE performs the energy scan and reports this
information to the eNodeB. If the band is available, the eNodeB can
then set-up communication in this shared band for V2V. If the band
is occupied, the eNodeB may decide to use a licensed cellular band
for operation.
[0266] While using a shared band for V2V, in mode 1 and mode 2, the
UE can perform an energy scan to sense potential collisions with
DSRC/IEEE 802.11p. If a DSRC signal is detected, the UE does not
transmit and defers all transmissions until the next available
opportunity. The UE also reports this information of a DSRC
transmission to the eNodeB at the next available opportunity. It
can be acceptable to ignore DSRC signals for aperiodic/emergency
messages to maintain critical safety functions in the shared
band.
[0267] Listen-before-talk (LBT) procedures defined for sharing
unlicensed spectrum with Wi-Fi can also be adopted for this
purpose. In one example, V2V based on SL can utilize an LAA when
operating on the same or adjacent band as DSRC/IEEE 802.11p. In
this case, V2V transmission authorization and load balancing
between available carriers for PC5 can be performed over control
signaling on licensed or dedicated V2V spectrum. For example, based
on energy sensing/RSSI measurements, channel occupancy, or other
mechanisms for detection of transmissions on a given carrier may be
used to determine to most suitable carrier for operation of one or
more V2V users/groups. Carrier selection average RSSI/channel
occupancy percentage thresholds may be configured or indicated by
higher layer signaling in the case of network-assisted V2V
operation including network selected and UE-autonomous resource
allocation. In addition, the existing LAA LBT protocol can be used
for SL transmissions. The high priority QoS class LBT parameters
may be applied to PC5 transmissions.
[0268] In another example, a new priority or QoS class may be
defined instead of the ones for non-PC5 based transmission.
Different LBT could be applied depending on traffic type (e.g.
event vs. periodic traffic) or physical channel (SA or data). TABLE
4 illustrates one example set of parameters.
TABLE-US-00004 TABLE 4 Channel Access Priority Class (p) m.sub.p
CW.sub.min,p CW.sub.max,p T.sub.mcol,p allowed CW.sub.p sizes
V2V_SA 1 1 1 1 ms {1} V2V_Event_data 1 2 3 1 ms {2, 3}
V2V_Periodic_data 1 3 7 1 ms {3, 7} 1 1 3 7 2 ms {3, 7} 2 1 7 15 3
ms {7, 15} 3 3 15 63 8 or 10 ms {15, 31, 63} 4 7 15 1023 8 or 10 ms
{15, 31, 63, 127, 255, 511, 1023}
[0269] In addition, a LBT without random backoff may be applied to
V2V transmissions. In one example, the V2V transmission may follow
after a fixed sensing interval (e.g. 16us, 25us, or 32us) applied
before one or more transmission instances (e.g. SL subframe or slot
boundary).
[0270] In another alternative, a hybrid channel access mechanisms
may be applied for V2V transmissions which utilizes a combination
of scheduling/resource pool configuration and LBT which can be more
efficient than fully distributed LBT. One of the advantages of SL
resource allocation is the use of periodic pools for control/data
messages which allow more efficient TDM/FDM multiplexing without
overhead associated with LBT/random backoff.
[0271] A resource pool containing multiple transmissions may be
configured containing multiple SA and data transmission
opportunities partitioned in a TDM or FDM manner and a sidelink
discovery beacon" (SDB) may precede the resource pool and provide
information about time-shifted resources pools depending on the
successful completion of an LBT procedure as described above. A
resource pool window may be defined for detection of the SDB based
on the configured periodicity. For example if the resource pool
periodicity is 20 ms, a resource pool window of 5 ms indicates that
a V2V UE may search for a SDB (and corresponding transmissions
within the subsequent resource pool) every 20 ms within a window of
5 ms (or 5 subframes).
[0272] If a transmission is not detected within the window, a UE
may wait until the next resource period to attempt to detect a SDB
or resource pool transmission. The resource pool window period and
duration may be preconfigured or indicated by broadcast or higher
layer signaling.
[0273] The SDB may contain one or more synchronization signals for
detection of the resource pool timing including periodicity,
duration, and time/frequency resources based on the sequence and/or
time frequency resources used. Alternatively, or in addition, a
sidelink discovery broadcast channel (SDBC) may be transmitted
which contains information related to the resource pool
configuration parameters including duration, periodicity, and
time/frequency resources, as well as LBT parameters, group
identifiers, and RS for demodulation of a SDBC message.
[0274] FIG. 26 illustrates an example operation of multiple
resource pools (RPs) 2600 according to embodiments of the present
disclosure. An embodiment of the operation of multiple RPs 2600
shown in FIG. 26 is for illustration only. Other embodiments may be
used without departing from the scope of the present
disclosure.
[0275] As shown in FIG. 26, the operation of multiple RPs 2600
comprises a V2V group 1 2605, a V2V group 2, and an IEEE
802.11p/DSRC. More specifically, FIG. 23 illustrates the operation
of multiple RPs including a SDB and SDBC transmission, and
co-existing with DSRC transmissions.
[0276] In one embodiment, the transmission power is semi-statically
configured by the eNB for a given resource pool. All UEs in a given
resource pool shall use the same transmission power. The transmit
power for PSSCH and PSCCH can be fixed for mode 2 operation in a
given resource pool. This can be done at least for the case, where
the V2V communication is using a dedicated channel and does not
need to co-exist with cellular communication on the same channel.
Since the traffic in a given geographical area is expected to be
correlated, the transmit power can be configured in a semi-static
manner in the resource pool. The transmit power for PSSCH and PSCCH
can be fixed in multiple ways. In one example, the transmit power
for PSSCH and PSCCH can be fixed always using the maximum transmit
power P.sub.PSCCH=P.sub.CMAX,PSCCH,
P.sub.PSSCH=P.sub.CMAX,PSSCH.
[0277] In another example, the transmit power for PSSCH and PSCCH
can be fixed using setting the bandwidth of the PSSCH and PSCCH
resource assignment expressed in number of resource blocks
M.sub.PSSCH and M.sub.PSCCH to a constant value in the resource
pool and setting the parameters .alpha..sub.PSSCH,2,
.alpha..sub.PSCCH,2 to 0 as given below:
P.sub.PSSCH=min{P.sub.CMAX,PSSCH,10
log.sub.10(M.sub.PSSCH)+P.sub.O.sub._.sub.PSSCH,2}
P.sub.PSSCH=min{P.sub.CMAX,PSSCH,10
log.sub.10(M.sub.PSSCH)+P.sub.O.sub._.sub.PSSCH,2}
[0278] In another embodiment, the transmission power per resource
block group (or per subchannel) is semi-statically configured by
the eNB. This configuration by the eNB could be based on parameters
such as the geo-graphical location (e.g., zone) or part of a
congestion control mechanism by the eNB based on measurement report
by the UEs to the eNB. All UEs in a given resource pool may use the
same transmit power per resource block group i.e. the power
spectral density (PSD) for transmission is kept constant within a
given resource pool.
[0279] This can help ensure that the energy sensing results can be
accurately compared across the different UEs. The transmit power
per resource block for PSSCH and PSCCH can be fixed for mode 2
operation in a given resource pool. This can be done at least for
the case, where the V2V communication is using a dedicated channel
and does not need to co-exist with cellular communication on the
same channel. The transmit power per resource block for PSSCH and
PSCCH can be fixed by setting the parameters .alpha..sub.PSSCH,2,
.alpha..sub.PSCCH,2 to 0.
[0280] In this case, the bandwidth of the PSSCH resource assignment
expressed in number of resource blocks M.sub.PSSCH need not be
fixed as given below
P.sub.PSSCH=min{P.sub.CMAX,PSSCH,10
log.sub.10(M.sub.PSSCH)+P.sub.O.sub._.sub.PSSCH,2}
P.sub.PSSCH=min{P.sub.CMAX,PSSCH,10
log.sub.10(M.sub.PSSCH)+P.sub.O.sub._.sub.PSSCH,2}
[0281] FIG. 27 illustrates an example transmit power per resource
block 2700 according to embodiments of the present disclosure. An
embodiment of the transmit power per resource block 2700 shown in
FIG. 27 is for illustration only. Other embodiments may be used
without departing from the scope of the present disclosure.
[0282] As illustrated in FIG. 27, the transmit power per resource
block 2700 comprises a plurality of UEs 2705 and 2710. More
specifically, FIG. 27 illustrates the transmit power per resource
block group P1 is kept fixed for all UEs 2705 and 2710 in a
resource block pool. i.e. the UE1 2705 and the UE2 2710 in the same
resource pool use the same transmit power per resource block group.
Since PSSCH and PSCCH can sensed separately and can use separate
resource pools, the transmission power per resource group for SA
pool and associated data pool can be independently configured.
[0283] During handover (HO), transmission and reception may
temporarily be interrupted. Following HO command, a source eNB
cannot schedule a UE anymore until HO has been successfully
completed. It is also assumed that after receiving HO command the
UE is not allowed to continue to select resources from a TX pool
configured by the source eNB. For mode 1, (exceptional) TX resource
pool configurations for the target cell can be signaled in the
handover command. If the (exceptional) TX resource pool is included
with mode 1 configuration into handover command, the UE starts the
(exceptional) TX resource pool from the reception of handover
command and continues it while T304 is running.
[0284] In one embodiment, when a UE receives a HO command, the UE
switches to use a separate resource pool identified for
transmissions in the handover phase irrespective of whether the UE
is configured for mode 1 or mode 2 operations. In order to reduce
sensing requirements for minimizing latency in this resource pool,
two options can be considered. In one example, the UE performs
random resource selection in this pool during HO (e.g., no
sensing). In another example, the UE performs partial sensing with
a reduced sensing window. For example, a sensing window of 100
sub-frames could be considered instead of 1 sec. The aforementioned
examples could be supported and indicated by the network.
[0285] The sensing window (or associated parameters for the sensing
window such as a, b) could also be indicated by the network. It is
also possible to support the aforementioned examples with a single
configuration. For example, if the sensing window is set to 0, the
UE performs random resource selection (i.e. no sensing).
[0286] V2V communication is initiated by transmission of a
synchronization SF that contains the master information block (MIB)
for SL communication. The sidelink common control information is
carried by a single message, the MasterInformationBlock-SL (MIB-SL)
message. The MIB-SL includes timing information as well as some
configuration parameters. The MIB-SL uses a fixed schedule with a
periodicity of 40 ms without repetitions. In particular, the MIB-SL
is scheduled in subframes indicated by syncOffsetIndicator i.e. for
which (10.times.DFN+subframe number) mod 40=syncOffsetIndicator.
The sidelink common control information may change at any
transmission i.e. neither a modification period nor a change
notification mechanism is used. The MIB-SL is transmitted in a SL
broadcast channel (PSBCH). The SF conveying the SBCH transmission
also conveys primary SL synchronization signals (PSSS) and
secondary SL synchronization signals (SSSS). In one example, the
MIB-SL transmission contains the system bandwidth (1.4, 3, 5, 10,
15 or 20 MHz). In another example, the MIB-SL transmission
contains, for TDD mode, the SF configuration that provides the SFs
used for UL transmissions and the SFs used for DL transmissions).
In yet another example, the MIB-SL transmission contains frame and
SF numbers of the SBCH, PSSS and SSSS transmission. In yet another
example, the MIB-SL transmission contains a Boolean flag indicating
whether the UE is within or outside NodeB coverage.
[0287] The format of the MIB-SL is as shown below:
[0288] MasterInformationBlock-SL
TABLE-US-00005 -- ASN1START MasterInformationBlock-SL::= SEQUENCE
{sl-Bandwidth-r12 ENUMERATED { n6, n15, n25, n50, n75, n100},
tdd-ConfigSL-r12 TDD-ConfigSL-r12, directFrameNumber-r12 BIT STRING
(SIZE (10)), directSubframeNumber-r12 INTEGER (0..9),
inCoverage-r12 BOOLEAN, reserved-r12 BIT STRING (SIZE (19)) } --
ASN1STOP
[0289] MasterInformationBlock-SL Field Descriptions: [0290]
directFrameNumber: Indicates the frame number in which SLSS and
SL-BCH are transmitted. The subframe in the frame corresponding to
directFrameNumber is indicated by directSubframeNumber. [0291]
inCoverage: Value TRUE indicates that the UE transmitting the
MasterInformationBlock-SL is in E-UTRAN coverage. [0292]
sl-Bandwidth Parameter: transmission bandwidth configuration. n6
corresponds to 6 resource blocks, n15 to 15 resource blocks and so
on.
TABLE-US-00006 [0292] TDD-ConfigSL-r12 ::= SEQUENCE {
subframeAssignmentSL-r12 ENUMERATED { none, sa0, sa1, sa2, sa3,
sa4, sa5, sa6} }
[0293] A total of 40 information bits (including 19 reserved bits)
are used for MIB-SL transmission.
[0294] FIG. 28 illustrates an example synchronization subframe (SF)
structure 2800 according to embodiments of the present disclosure.
An embodiment of the synchronization SF structure 2800 shown in
FIG. 28 is for illustration only. Other embodiments may be used
without departing from the scope of the present disclosure.
[0295] As shown in FIG. 28, a number of 6 PRBs (or 72 sub-carriers)
are used for PSBCH transmission. The MIB-SL information is
transmitted on 7 PSBCH symbols, after adding a 16-bit CRC,
scrambling, channel coding with a rate 1/3 tail-biting
convolutional code (TBCC), rate-matching and mapping with QPSK
modulation. Sidelink synchronization signals (SLSS) include two
signals: the PSSS and the SSSS. PSSS and SSSS are both transmitted
in adjacent time slots in a same SF.
[0296] The PSBCH and synchronization signals always use the same
cyclic prefix. The PSBCH uses the same set of resource blocks as
the synchronization signal. The combination of both signals defines
a "Sidelink ID" (SID) N.sub.ID.sup.SL, similar to the "Physical
Cell ID" in the DL. SIDs are split into two sets. SIDs in the range
of {0, 1, . . . , 167) are reserved for `in-coverage` operation,
where {168, 169, . . . , 335} are used when a device is
`out-of-coverage`. In the case of extended CP configuration, where
only 13 symbols are available, the frame structure of the normal CP
is used excluding the first symbol in the normal CP case.
[0297] The sequence d(n) used for the PSSS is generated from a
frequency-domain Zadoff-Chu sequence according to:
d u ( n ) = { e - j .pi. un ( n + 1 ) 63 n = 0 , 1 , 30 e - j .pi.
u ( n + 1 ) ( n + 2 ) 63 n = 31 , 32 , 61 ##EQU00001##
where u is the Zadoff-Chu root sequence index.
[0298] Each of the two sequences d.sub.i (0), . . . , d.sub.i (61),
i=1, 2 used for the PSSS in the two SC-FDMA symbols is given by
Equation 1 with root index u=26 if N.sub.ID.sup.SL.ltoreq.167 and
u=37 otherwise. The sequence d(0), . . . , d(61) used for the
second synchronization signal (SSS) is an interleaved concatenation
of two length-31 binary sequences. The concatenated sequence is
scrambled with a scrambling sequence given by the primary
synchronization signal.
[0299] The combination of two length-31 sequences defining the
secondary synchronization signal differs between subframes
according to:
d ( 2 n ) = { s 0 ( m 0 ) ( n ) c 0 ( n ) in subframes 0 , 1 , 2 ,
3 , 4 s 1 ( m 1 ) ( n ) c 0 ( n ) in subframes 5 , 6 , 7 , 8 , 9 d
( 2 n + 1 ) = { s 1 ( m 1 ) ( n ) c 1 ( n ) z 1 ( m 0 ) ( n ) in
subframes 0 , 1 , 2 , 3 , 4 s 0 ( m 0 ) ( n ) c 1 ( n ) z 1 ( m 1 )
( n ) in subframes 5 , 6 , 7 , 8 , 9 ##EQU00002##
[0300] where 0.ltoreq.n.ltoreq.30.
[0301] The indices m.sub.0 and m.sub.1 are derived from the
physical-layer cell-identity group N.sub.ID.sup.(1) according
to:
m 0 = m ' mod 31 ##EQU00003## m 1 = ( m 0 + m ' / 31 + 1 ) mod 31
##EQU00003.2## m ' = N ID ( 1 ) + q ( q + 1 ) / 2 , q = N ID ( 1 )
+ q ' ( q ' + 1 ) / 2 30 , q ' = N ID ( 1 ) / 30 ##EQU00003.3##
[0302] The two sequences)s.sub.0.sup.(m.sup.0.sup.)(n) and
s.sub.1.sup.(m.sup.1.sup.)(n) are defined as two different cyclic
shifts of the m-sequence {tilde over (s)}(n) according to
s.sub.0.sup.(m.sup.0.sup.)(n)={tilde over (s)}((n+m.sub.0)mod
31)
s.sub.0.sup.(m.sup.1.sup.)(n)={tilde over (s)}((n+m.sub.1)mod
31)
where {tilde over (s)}(i)=1-2x(i), 0.ltoreq.i.ltoreq.30, is defined
by x( +5)=(x( +2)+x( ))mod 2, 0< .ltoreq.25 with initial
conditions x(0)=0, x(1)=0, x(2)=0, x(3)=0, x(4)=1.
[0303] The two scrambling sequences c.sub.0(n) and c.sub.1(n)
depend on the primary synchronization signal and are defined by two
different cyclic shifts of the m-sequence {tilde over (c)}(n)
according to:
c.sub.0(n)={tilde over (c)}((n+N.sub.ID.sup.(2))mod 31)
c.sub.1(n)={tilde over (c)}((n+N.sub.ID.sup.(2)+3)mod 31)
where N.sub.ID.sup.(2).epsilon.{0, 1, 2} is the physical-layer
identity within the physical-layer cell identity group
N.sub.ID.sup.(1) and {tilde over (c)}(i)=1-2x(i),
0.ltoreq.i.ltoreq.30, is defined by x( +5)=(x( +3)+x( ))mod 2, 0
.ltoreq.25 with initial conditions x(0)=0, x(1)=0, x(2)=0, x(3)=0,
x(4)=1.
[0304] The scrambling sequences z.sub.1.sup.(m.sup.0.sup.)(n) and
z.sub.1.sup.(m.sup.1.sup.)(n) are defined by a cyclic shift of the
m-sequence {tilde over (z)}(n) according to:
z.sub.1.sup.(m.sup.0.sup.)(n)={tilde over (z)}((n+(m.sub.0 mod
8))mod 31)
z.sub.1.sup.(m.sup.1.sup.)(n)={tilde over (z)}((n+(m.sub.1 mod
8))mod 31)
where m.sub.0 and m.sub.1 are obtained from LTE specification and
{tilde over (z)}(i)=1-2(i), 0.ltoreq.i.ltoreq.30, is defined by x(
+5)=(x( +4)+x( +2)+x( +1)+x( ))mod 2, 0.ltoreq.i.ltoreq.25 with
initial conditions x(0)=0, x(1)=0, x(2)=0, x(3)=0, x(4)=1.
[0305] For sidelink, subframe 0 with
N.sub.ID.sup.(1)=N.sub.ID.sup.SL mod 168 and N.sub.ID.sup.(2)=.left
brkt-bot.N.sub.ID.sup.SL/168.right brkt-bot. is assumed, where
N.sub.ID.sup.SL is the SLSS ID used for SL.
[0306] The SFs, a UE can use to transmit SLSS and PSBCH, are
configured to the UE by higher layers. There is no physical SL
shared channel (PSSCH), physical SL control channel (PSCCH) or
physical SL discovery channel (PSDCH) transmissions in the SFs
configured for SLSS and PSBCH transmission. The PSSS and SSSS are
repeated twice and use 62 sub-carriers. The synchronization SF
includes DMRS transmission in two symbols (denoted as 2V
structure). The DMRS can be used for channel estimation or for
carrier frequency offset (CFO) correction at a UE receiver. The
last symbol in a SL SF serves as a guard period and is not used for
SL transmission. The synchronization SF is transmitted every 40
msec.
[0307] FIG. 29 illustrates an example transmitter for
synchronization operation in vehicle-to-vehicle (V2V)
communications 2900 according to embodiments of the present
disclosure. An embodiment of the transmitter for synchronization
operation in V2V communications shown in FIG. 29 is for
illustration only. Other embodiments may be used without departing
from the scope of the present disclosure.
[0308] As shown in FIG. 29, the 40 MIB-SL information bits are
appended with a 16-bit CRC and scrambled based on the SL ID. The
scrambled bits are then encoded with a rate 1/3 tail-biting
convolutional code, interleaved and rate matched to 1008 bits that
are mapped to 504 QPSK symbols. The IDFT filter maps the 504 QPSK
symbols to 7 SF symbols with 72 sub-carriers per symbol. The DMRS
and the PSSS/SSSS symbols are multiplexed with the MIB-SL symbols
to form the SF. These symbols are then converted to the time-domain
via an IFFT filter and transmitted. Although only a single antenna
is shown in FIG. 29, multiple antennas can also be considered to
provide diversity at the transmitter.
[0309] FIG. 30 illustrates an example receiver for synchronization
operation in vehicle-to-vehicle (V2V) communications 3000 according
to embodiments of the present disclosure. An embodiment of the
receiver for synchronization operation in V2V communications 3000
shown in FIG. 30 is for illustration only. Other embodiments may be
used without departing from the scope of the present
disclosure.
[0310] As shown in FIG. 30, the receiver uses the PSSS/SSSS to
obtain synchronization and to detect a SL ID. The receiver uses the
DMRS for channel estimation and for CFO estimation and correction.
Since the PSSS and SSSS are repeated, they can also be used for CFO
estimation. After equalization and IDFT filtering, the log
likelihood ratios (LLRs) are computed for the 504 QPSK symbols
transmitted in the PSBCH. The LLRs are then combined during rate
matching and are subsequently decoded. The decoded bits are
descrambled with the SL ID and the CRC is checked to determine
whether or not the received bits have been decoded correctly.
Although only a single antenna is shown in FIG. 30, multiple
antennas can also be considered to provide diversity at the
receiver.
[0311] FIG. 31 illustrates an example channel coherence time 3100
according to embodiments of the present disclosure. An embodiment
of the channel coherence time 3100 shown in FIG. 31 is for
illustration only. Other embodiments may be used without departing
from the scope of the present disclosure. As shown in FIG. 31, the
DMRS symbols in the PSBCH in 3GPP Rel-13 are separated by 0.5 msec.
This time separation can be sufficient for channel estimation when
a carrier frequency is in the range of 2 GHz as the channel
coherence time exceeds the DMRS spacing in time. However, carrier
frequencies considered for V2V communication include a frequency
band at 5.9 GHz (5.850-5.925 GHz) that is allocated for dedicated
short range communications (DRSC) and can be used for vehicular
communication. For such carrier frequencies, the Doppler shift can
result to a channel coherence time that is smaller than the DMRS
spacing and this adversely impacts channel estimation and decoding
of the PSBCH. Referring to FIG. 31, a channel coherence time for a
carrier frequency of 2 GHz and for a carrier frequency of 5.9 GHz
as a function of the UE speed are illustrated. From FIG. 30, it can
be observed that the channel coherence time is less than the DMRS
spacing for UE speeds above 140 Km/h at 5.9 GHz. Therefore, a DMRS
spacing of 0.5 msec is not sufficient for V2V communications at 5.9
GHz and this motivates a redesign for the PSBCH DMRS.
[0312] There is also a need to distinguish the synchronization
signals for V2V communication from that of D2D. Hence, the PSSS and
SSSS designs need to be reconsidered for V2V communication. There
is another need to enable a UE to perform CFO estimation and
correction. Finally, there is a need to enable target reception
reliability for a MIB-SL at high vehicular speeds.
[0313] Since the V2V communication protocol is assumed to be based
on the 3GPP D2D protocol design, the case where D2D and V2V share
the same network and carrier frequency is considered. In this case,
there can be applications where the D2D and V2V networks are
separate networks and do not need to interact with each other. In
other cases, there can be applications where vehicles communicate
with devices/pedestrians (as in a V2P network) that in turn can
talk to other devices using D2D communications.
[0314] In one embodiment, the V2V and D2D networks are
distinguished by the use of different synchronization signals. Only
the PSSS is modified using two different Zadoff-Chu root sequence
indices for in network operation and for out of network operation
in V2V communication compared to D2D. The SSSS for D2D is re-used.
The two different Zadoff-Chu root sequence indices are selected
based on properties of small auto and cross correlations and low
frequency offset sensitivity. The combination of the PSSS and SSSS
provides the SL ID for V2V communication. The detection of the PSSS
also informs the vehicle that the synchronization SF structure for
V2V, not for D2D, is to be used as well as the new locations for
the DMRS and PSBCH symbols (compared to the D2D SF structure).
[0315] FIG. 32 illustrates an example V2V and D2D network operation
3200 according to embodiments of the present disclosure. An
embodiment of the V2V and D2D network operation 3200 shown in FIG.
32 is for illustration only. Other embodiments may be used without
departing from the scope of the present disclosure.
[0316] As shown in FIG. 32, the vehicle UEs and the mobile UEs are
part of the same network 3201. A vehicle UE 3202 communicates with
a vehicle UE 3203 using a V2V SL protocol while a mobile UE 3204
communicates with a mobile UE 3205 using a D2D SL protocol. The
networks are distinguished by the use of separate PSSS that are
generated by Zadoff-Chu sequences that have different root indices.
For D2D operation, root index u1=26 is used if
N.sub.ID.sup.SL.ltoreq.167 for in network operation and u2=37 is
used otherwise. For V2V operation, new root indices u3 and u4 are
used and they can be selected to have low cross-correlation with u1
and u2.
[0317] FIG. 33 illustrates another example V2V and D2D network
operation 3300 according to embodiments of the present disclosure.
An embodiment of the V2V and D2D network operation 3300 shown in
FIG. 33 is for illustration only. Other embodiments may be used
without departing from the scope of the present disclosure.
[0318] As shown in FIG. 33, the vehicle UEs and mobile UEs are part
of a same network 3301. A vehicle UE 3302 communicates with a
vehicle UE 3303 using a V2V SL protocol while a mobile UE 3305
communicates with a mobile UE 3304 using a D2D SL protocol. The
vehicle UE 3302 also communicates with the mobile UE 3304 using SL
V2P. The networks are distinguished by the use of separate PSSS
that are generated by respective Zadoff-Chu sequences that have
different root indices. However, the SL IDs in this case cannot
overlap to avoid possible collisions of transmissions from a
vehicle UE and a mobile UE using a same SL ID. Hence, SL IDs from
{336, 337, . . . 671} can be used for V2V operation while {0, 1, .
. . , 335} can be reserved for D2D operation. For D2D operation,
root index u1=26 is used if N.sub.ID.sup.SL.ltoreq.167 for in
network operation and u2=37 is used otherwise. For V2V operation,
new root indices u3 is used if N.sub.ID.sup.SL.ltoreq.503 for in
network operation and u4 is used otherwise. The new root indices u3
and u4 can be selected to have low cross-correlation with u1 and
u2. Once a UE detects a SL ID from {336 through 671}, the UE
interprets a V2V transmission and considers different locations for
the DMRS and the PSBCH symbols in the synchronization relative to
the locations used for a D2D transmission.
[0319] In some embodiments, the synchronization signals are not
changed from legacy D2D synchronization signals. This can be done
for backward compatibility with D2D when shared carriers are used
and the operator may want to configure the network for V2V and D2D
operation dynamically. In such embodiments, the V2V and D2D
networks can be distinguished by using separate SL IDs generated by
the same PSSS and SSSS transmissions as legacy D2D, which can
generate a different scrambling pattern compared to legacy D2D.
[0320] SL IDs from {336, 337, . . . 671} can be used for V2V
operation while {0, 1, . . . , 335} can be reserved for D2D
operation. The SL IDs for V2V are generated by adding 336 to the SL
IDs for D2D operation. Since the legacy PSSS signals are not
changed for V2V operation, legacy root indices u1 is used if
N.sub.ID.sup.SL.ltoreq.503 for in network operation and legacy root
u2 is used otherwise. The PSBCH for V2V is scrambled with the new
V2V SL IDs. Thus, legacy D2D networks may not be able to decode the
PSBCH contents from V2V traffic. Devices that support both V2V and
D2D can however decode both D2D and V2V data. The new receiver that
supports both D2D and V2V can blindly decode the PSBCH by using
both the old and new SL IDs after synchronization i.e. SL ID `x`
and SLID `x+336`.
[0321] In order to support GNSS or GNSS equivalent based operation,
where the concept of separate SL IDs is not required since the
whole network can be synchronized irrespective of a cell, a single
SL ID can be reserved that is outside the range of the existing SL
IDs for V2V and D2D. In one example, a value of {672} can be
reserved for GNSS based V2V operation. For GNSS, legacy root
indices u1 is used for in network operation and legacy root u2 is
used otherwise. The SSSS for SL ID 0 can be used for GNSS
operation, for example, since only a single SL ID is required. In
such example, 3 blind decodes are required if the SSSS for SL ID of
0 is used (0, 336, 672) and 2 blind decodes are required
otherwise.
[0322] Since synchronization sources within the same cell can be
SFN accumulated, the D2D and V2V synchronization may be separated
to avoid the interference between D2D and V2V due to different
PSBCH structure. If SLSS transmitted by vehicle is identical as
D2D, and uses different synchronization resource from D2D, then
inter cell discovery reception for the D2D discovery UE can be
impacted as well. This implies Rel-13 D2D receiver may not detect
Rel-14 V2V sync transmissions and that Rel-14 V2V receiver may not
detect Rel-13 D2D sync transmissions. Hence SLSS may be
differentiated between Rel-14 V2V and Rel-13 D2D.
[0323] In some embodiments, the SLSS for V2V and D2D networks are
differentiated by using different scrambling sequences for V2V
derived from the new SLSS IDs for V2V. Based on the new SLSS ID for
V2V, the two scrambling sequences c.sub.0(n) and c.sub.1(n), which
depend on the primary synchronization signal and are defined by two
different cyclic shifts of the m-sequence {tilde over (c)}(n)
according to:
{tilde over (c)}.sub.0(n)={tilde over (c)}((n+N.sub.ID.sup.(2))mod
31)
{tilde over (c)}.sub.1(n)={tilde over
(c)}((n+N.sub.ID.sup.(2)+3)mod 31)
where N.sub.ID.sup.(2)=.left brkt-bot.N.sub.ID.sup.SL/168.right
brkt-bot. is assumed and {tilde over (c)}(i)=1-2x(i),
0.ltoreq.i.ltoreq.30, is defined by x( +5)=(x( +3)+x( ))mod 2,
0.ltoreq. .ltoreq.25 with initial conditions x(0)=0, x(1)=0,
x(2)=0, x(3)=0, x(4)=1.
[0324] Since N.sub.ID.sup.SL now different for V2V vs. D2D due to
new SLSS IDs, N.sub.ID.sup.(2) is now different, which leads to two
different scrambling sequences c.sub.0(n) and c.sub.1(n) for V2V
that ensures that D2D receiver cannot detect the new V2V SSSS
transmissions. Thus, D2D and V2V SLSS can be differentiated.
[0325] In some embodiments, the SLSS for V2V and D2D networks are
differentiated by using different scrambling sequences derived from
using the same SLSS ID for D2D. Two scrambling sequences c.sub.0
(n) and c.sub.1(n), which depend on the primary synchronization
signal and are defined by two different cyclic shifts of the
m-sequence c (n) according to:
c.sub.0(n)={tilde over (c)}((n+N.sub.ID.sup.(2)+a)mod 31)
c.sub.1(n)={tilde over (c)}((n+N.sub.ID.sup.(2)+b)mod 31)
where N.sub.ID.sup.(2)=.left brkt-bot.N.sub.ID.sup.SL/168.right
brkt-bot. and a, b are integer offsets where a is assumed and
{tilde over (c)}(i)=1-2x(i), 0.ltoreq.i.ltoreq.30, is defined by x(
+5)=(x( +3)+x( ))mod 2, 0.ltoreq. .ltoreq.25 with initial
conditions x(0)=0, x(1)=0, x(2)=0, x(3)=0, x(4)=1.
[0326] The offsets a and b are chosen such that the offsets a and b
lead to two different scrambling sequences c.sub.0(n) and
c.sub.1(n) for V2V that ensures that D2D receiver cannot detect the
new V2V SSSS transmissions. Thus, D2D and V2V SLSS can be
differentiated.
[0327] In some embodiments, the SLSS for V2V and D2D networks are
differentiated by using different scrambling sequences derived from
using the same SLSS ID for D2D. Two scrambling sequences c.sub.0(n)
and c.sub.1(n), which depend on the primary synchronization signal
and are defined by two different cyclic shifts of the m-sequence c
(n) according to:
c.sub.0(n)={tilde over (c)}((n+N.sub.ID.sup.(2))mod 31)
c.sub.1(n)={tilde over (c)}((n+N.sub.ID.sup.(2)+3)mod 31)
where N.sub.ID.sup.(2)=.left brkt-bot.N.sub.ID.sup.SL/168.right
brkt-bot. and {tilde over (c)}(i)=1-2x(i), 0.ltoreq.i.ltoreq.30 are
defined according to a different scrambling sequence c.sub.0(n) and
c.sub.1(n) that ensures that D2D receiver cannot detect the new V2V
SSSS transmissions.
[0328] This can be done for example, by a different mapping for x
than that used for D2D and/or by different initial conditions than
that used for D2D. This leads to two different scrambling sequences
c.sub.0(n) and c.sub.1(n) for V2V that ensures that D2D receiver
cannot detect the new V2V SSSS transmissions. Thus, D2D and V2V
SLSS can be differentiated.
[0329] In some embodiments, the SF structure for PSBCH is modified
for V2V communication by modifying a location for DMRS symbols and
for PSBCH symbols.
[0330] FIG. 34 illustrates an example physical sidelink broadcast
channel (PSBCH) SF structure for V2V 3400 according to embodiments
of the present disclosure. An embodiment of the PSBCH SF structure
for V2V 3400 shown in FIG. 34 is for illustration only. Other
embodiments may be used without departing from the scope of the
present disclosure.
[0331] As shown in FIG. 34, DMRS symbols are placed in symbols 5
and 8 (symbol indexing starts from 0) in the SF. The location of
the DMRS symbols can allow a UE to estimate a channel over larger
Doppler shifts at 5.9 GHz. For example, a CFO for PSBCH symbols 0
and 3 can be estimated using the PSSS, a CFO for PSBCH symbols 4,
6, 7, 9 can be estimated using the DMRS, and a CFO for PSBCH symbol
10 can be estimated using the SSSS. In the case of extended CP
configuration, where only 13 symbols are available, the frame
structure of the normal CP is used excluding the first symbol in
the normal CP case, similar to the legacy frame structure for
extended CP.
[0332] In some embodiments, additional DMRS symbols are included in
a PSBCH SF. This can improve channel estimation and CFO correction
at a cost of reducing a number of available symbols for PSBCH
transmission.
[0333] FIG. 35 illustrates an example PSBCH SF structure with
additional demodulation reference signal (DMRS) symbols 3500
according to embodiments of the present disclosure. An embodiment
of the PSBCH SF structure with additional DMRS symbols 3500 shown
in FIG. 35 is for illustration only. Other embodiments may be used
without departing from the scope of the present disclosure.
[0334] As shown in FIG. 35, an additional DMRS symbol is
transmitted in symbol 6 (3V structure). Alternatively, symbol 7 can
be used instead of symbol 6 for the additional DMRS symbol.
[0335] FIG. 36 illustrates another example PSBCH SF structure with
additional demodulation reference signal (DMRS) symbols 3600
according to embodiments of the present disclosure. An embodiment
of the PSBCH SF structure with additional DMRS symbols 3600 shown
in FIG. 36 is for illustration only. Other embodiments may be used
without departing from the scope of the present disclosure.
[0336] As shown in FIG. 36, two additional DMRS symbols are
transmitted in symbols 6 and 7 to improve CFO estimation and
correction.
[0337] FIG. 37 illustrates yet another example PSBCH SF structure
with additional DMRS symbols 3700 according to embodiments of the
present disclosure. An embodiment of the PSBCH SF structure with
additional DMRS symbols 3700 shown in FIG. 37 is for illustration
only. Other embodiments may be used without departing from the
scope of the present disclosure. As shown in FIG. 37, two
additional DMRS symbols are transmitted in symbols 0 and 6 (or 7)
to improve CFO estimation and correction. Relative to FIG. 36, the
PSBCH symbols are kept closer in time and a channel variation can
be smaller during the duration of the PSBCH transmission.
[0338] FIG. 38 illustrates another example PSBCH SF structure 3800
according to embodiments of the present disclosure. An embodiment
of the PSBCH SF structure 3800 shown in FIG. 38 is for illustration
only. Other embodiments may be used without departing from the
scope of the present disclosure.
[0339] The aforementioned embodiments considered the case where the
PSSS and SSSS locations are not changed. Further performance
enhancements can be obtained by changing the location of the PSSS
symbols so that the PBSCH symbols are closer to each other in the
subframe. As shown in FIG. 38, PSSS is now sent at symbol 0 and
symbol 1 instead of symbol 1 and symbol 2 of the subframe. Relative
to FIG. 36, the PSBCH symbols are kept closer in time and a channel
variation can be smaller during the duration of the PSBCH
transmission.
[0340] FIG. 39 illustrates yet another example PSBCH SF structure
with additional DMRS symbols 3900 according to embodiments of the
present disclosure. An embodiment of the PSBCH SF structure with
additional DMRS symbols 3900 shown in FIG. 39 is for illustration
only. Other embodiments may be used without departing from the
scope of the present disclosure.
[0341] As shown in FIG. 39, due to the high Doppler, it may be
difficult to compensate for the PSBCH symbol 0 and this symbol may
be punctured. Instead, an additional PSSS sequence could be
transmitted at symbol 0, which can help with increased reliability
of CFO estimation.
[0342] In some embodiments, the 1.sup.st SC-FDMA symbol (symbol 0)
to be used for PSSS transmission for V2V communication may be used.
In such embodiments, the PSBCH may be grouped together in the
center, allowing better compensation for Doppler and provide better
CFO and timing estimation by transmitting an additional PSSS
sequence. Note that the DMRS locations used in FIG. 39 are just
exemplary and the PSSS transmission on the 1.sup.st symbol (symbol
0) is independent of the choice of DMRS configuration for PSBCH
transmission.
[0343] FIG. 40 illustrates yet another example PSBCH SF st h
additional
[0344] DMRS symbols 4000 according to embodiments of the present
disclosure. An embodiment of the PSBCH SF structure with additional
DMRS symbols 4000 shown in FIG. 40 is for illustration only. Other
embodiments may be used without departing from the scope of the
present disclosure.
[0345] FIG. 41 illustrates yet another example PSBCH SF structure
with additional DMRS symbols 4100 according to embodiments of the
present disclosure. An embodiment of the PSBCH SF structure with
additional DMRS symbols 4100 shown in FIG. 41 is for illustration
only. Other embodiments may be used without departing from the
scope of the present disclosure.
[0346] As shown in FIG. 40 and FIG. 41, respectively, the DMRS is
sent in all PSBCH data symbols in certain fixed frequency locations
for improved support for Doppler for speeds up to 500 km/h.
[0347] In some embodiments, the number of DMRS symbols used for
PSBCH is made configurable due to the high overhead of DMRS symbols
in the subframe, since these additional symbols are only needed for
high frequency (6 GHz vs. 2 GHz) and for high speed scenarios. In
one example, at 2 GHz frequency band, only 2 DMRS symbols may be
used while at 6 GHz, there may be 3 DMRS symbols used. In another
example, at 30 km/h only 2 DMRS symbols are used vs. 3 DMRS symbols
are used at 140 km/h.
[0348] In some embodiments, the DMRS symbols is punctured to
achieve the configurability when not required to support high speed
or high carrier frequency and data in those locations, as needed,
is sent, where the data is rate matched accordingly to use the
extra symbol or symbols. When puncturing is performed, it can be
done on the inner DMRS symbol or symbols.
[0349] In some embodiments, the eNodeB sidelink configuration is
achieved for the UE, where the eNodeB informs the UE to select one
of multiple available DMRS configuration patterns. In some
embodiments, the control channel such as PSBCH and/or PSCCH could
have a fixed DMRS configuration. However, the data shared channel
such as PSSCH could have a variable DMRS configuration where the
DMRS setting is indicated by setting at least one bit in the
control channel. The UE, depending on its current speed and its
carrier frequency, indicates the DMRS configuration for PSCCH in
its control transmissions. The UE can make this decision
independently in Mode 2 sidelink operation or the UE could make
decision as part of a message from the eNodeB. Thus, the DMRS
configuration can by RRC for both control/data or by RRC/fixed for
control and dynamic for data.
[0350] In some embodiments, only the PSBCH uses a fixed number of
DMRS resources. However, both the data shared channel (PSSCH) and
the control channel (PSCCH) can have a variable DMRS configuration
where the DMRS configuration is indicated by setting one bit in the
MIB-SL or by RRC signaling. Support for variable DMRS configuration
enables the system to be more efficient when high Doppler support
is not required.
[0351] FIG. 42 illustrates an example DMRS configuration for
physical sidelink shared channel (PSSCH) and physical sidelink
control channel (PSCCH) 4200 according to embodiments of the
present disclosure. An embodiment of the DMRS configuration for
PSSCH and PSCCH 4200 shown in FIG. 42 is for illustration only.
Other embodiments may be used without departing from the scope of
the present disclosure.
[0352] FIG. 42 shows the DMRS configuration for PSSCH and PSCCH
indicated via using a bit in the MIB-SL (PSBCH transmission) or by
RRC signaling, according to the embodiments of this disclosure.
Based on the configuration, either 2 DMRS symbols (2V) or 4 DMRS
symbols (4V) are used for transmission of PSSCH and PSCCH. The DMRS
structure (e.g. reference symbol design) for the 4V configuration
need not be identical to the DMRS structure for the 2V
configuration. The eNB can configure the DMRS based on the carrier
frequency and/or current geo location or zone.
[0353] In one example, a 2V structure for DMRS is chosen when the
carrier frequency is 2 GHz while a 4V structure for DMRS is chosen
when the carrier frequency is 6 GHz. In another example, a 2V
structure is chosen when the UE is in an urban geolocation zone
with low traffic speeds while a 4V structure is chosen in a zone
associated with a freeway or fast traffic speeds. The UE indicates
the chosen DMRS configuration for PSCCH and PSSCH transmissions in
the MIB-SL when PSBCH is transmitted. The DMRS configuration for
PSCCH and PSSCH transmissions can be set directly via RRC signaling
when PSBCH is not transmitted (for example, when in coverage or
Mode 1). Alternatively, the UE can also perform PSCCH decoding
blindly based on the two DMRS structure options and use the DMRS
pattern that resulted in the successful decode of the PSCCH for
decoding the PSSCH.
[0354] In some embodiments, an additional bit of information is
transmitted in the MIB-SL to indicate V2V support according to
illustrative embodiments of the present disclosure. The format of
the MIB-SL is as subsequently described:
[0355] MasterInformationBlock-SL
TABLE-US-00007 -- ASN1START MasterInformationBlock-SL ::= SEQUENCE
{ sl-Bandwidth-r14 ENUMERATED {n6, n15, n25, n50, n75, n100},
tdd-ConfigSL-r14 TDD-ConfigSL-r14, directFrameNumber-r14 BIT STRING
(SIZE (10)), directSubframeNumber-r14 INTEGER (0..9),
inCoverage-r14 BOOLEAN, GNSS-sync-r14 BOOLEAN, V2V-r14 BOOLEAN,
DMRSConfig-r14 BOOLEAN, reserved-r14 BIT STRING (SIZE (16)) } --
ASN1STOP
[0356] The V2V field is used to identify that the transmitting
device is intending V2V communications as shown: [0357]
V2V-r14=0=>D2D transmission [0358] V2V-r14=1=>V2V
transmission
[0359] The GNSS-sync field is used to identify if the
synchronization is obtained through the network or via GNSS (or
GNSS equivalent) as shown: [0360] GNSS-sync-r14=0=>NodeB is the
synchronization source [0361] GNSS-sync-r14=1=>GNSS or
GNSS-equivalent is the synchronization source
[0362] The DMRSConfig field is used to indicate whether 2V DMRS
structure or 4V DMRS structure is used for PSSCH and PSCCH
transmissions as shown: [0363] DMRSConfig=0=>2V DMRS structure
is used for PSSCH and PSCCH transmissions [0364]
DMRSConfig=1=>4V DMRS structure is used for PSSCH and PSCCH
transmissions
[0365] In some embodiments, the repetition period for the
synchronization SF is decreased from once every 40 msec to a
reduced periodicity such as once every 10 msec (1 frame). The
repetition period is decreased to support lower latency
requirements as well as increased reliability of transmissions.
This can be signaled by modifying the sidelink communication period
information element to use at least one of the spare bits to signal
a shorter periodicity such as a 10 msec or 20 msec repetition as
shown:
TABLE-US-00008 -- ASN1START SL-PeriodComm-r14 ::= ENUMERATED {sf40,
sf60, sf70, sf80, sf120, sf140, sf160, sf240, sf280, sf320, sf20,
sf10, spare4, spare3, spare2, spare} -- ASN1STOP
[0366] None of the description in this application should be read
as implying that any particular element, step, or function is an
essential element that must be included in the claim scope. The
scope of patented subject matter is defined only by the claims.
Moreover, none of the claims is intended to invoke 35 U.S.C.
.sctn.112(f) unless the exact words "means for" are followed by a
participle.
* * * * *